Piezoelectric/electrostrictive device and method of manufacturing same

ABSTRACT

A piezoelectric/electrostrictive device comprises a pair of mutually opposing thin plate sections and a fixation section for supporting the thin plate sections; and a piezoelectric/electrostrictive element arranged on each of the pair of thin plate sections; wherein movable sections have mutually opposing end surfaces; and a distance between the end surfaces is not less than a length of the movable section.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a piezoelectric/electrostrictivedevice which is provided with a movable section to be operated on thebasis of a displacement action of a piezoelectric/electrostrictiveelement, or a piezoelectric/electrostrictive device which is capable ofdetecting displacement of a movable section by the aid of apiezoelectric/electrostrictive element, and a method for producing thesame. In particular, the present invention relates to apiezoelectric/electrostrictive device which is excellent in strength,shock resistance, and moisture resistance and which makes it possible toefficiently operate a movable section to a great extent, and a methodfor producing the same.

[0003] 2. Description of the Related Art

[0004] Recently, a displacement element, which makes it possible toadjust the optical path length and the position in an order ofsubmicron, is required, for example, in the fields of the optics, themagnetic recording, and the precision machining. Development is advancedfor the displacement element based on the use of the displacementbrought about by the inverse piezoelectric effect or theelectrostrictive effect caused when a voltage is applied to apiezoelectric/electrostrictive material (for example, a ferroelectricmaterial).

[0005] As shown in FIG. 41, for example, those hitherto disclosed assuch a displacement element include a piezoelectric actuator comprisinga fixation section 204, a movable section 206, and a beam section 208for supporting them which are formed in an integrated manner with a hole202 provided through a plate-shaped member 200 composed of apiezoelectric/electrostrictive material and with an electrode layer 210provided on the beam section 208 (see, for example, Japanese Laid-OpenPatent Publication No. 10-136665).

[0006] The piezoelectric actuator is operated such that when a voltageis applied to the electrode layer 210, the beam section 208 makesexpansion and contraction in a direction along a line obtained byconnecting the fixation section 204 and the movable section 206 inaccordance with the inverse piezoelectric effect or the electrostrictiveeffect. Therefore, the movable section 206 can perform circulararc-shaped displacement or rotational displacement in the plane of theplate-shaped member 200.

[0007] On the other hand, Japanese Laid-Open Patent Publication No.63-64640 discloses a technique in relation to an actuator based on theuse of a bimorph. In this technique, electrodes for the bimorph areprovided in a divided manner. The actuator is driven due to theselection of the divided electrodes, and thus the highly accuratepositioning is performed at a high speed. This patent document(especially in FIG. 4) discloses a structure in which, for example, twobimorphs are used in an opposed manner.

[0008] However, the piezoelectric actuator described above involves sucha problem that the amount of operation of the movable section 206 issmall, because the displacement in the direction of expansion andcontraction of the piezoelectric/electrostrictive material (i.e., in thein-plane direction of the plate-shaped member 200) is transmitted to themovable section 206 as it is.

[0009] All of the parts of the piezoelectric actuator are made of thepiezoelectric/electrostrictive material which is a fragile materialhaving a relatively heavy weight. Therefore, the following problemsarise. That is, the mechanical strength is low, and the piezoelectricactuator is inferior in handling performance, shock resistance, andmoisture resistance. Further, the piezoelectric actuator itself isheavy, and its operation tends to be affected by harmful vibrations (forexample, residual vibration and noise vibration during high speedoperation).

[0010] In order to solve the problems described above, it has beensuggested that the hole 202 is filled with a filler material havingflexibility. However, it is clear that the amount of displacement, whichis brought about by the inverse piezoelectric effect or theelectrostrictive effect, is decreased even when the filler material ismerely used.

[0011] Further, the actuator described in Japanese Laid-Open PatentPublication No. 63-64640 has such a structure that the bimorph itself iscomposed of two piezoelectric elements which are laminated with eachother, in addition to the fact that the bimorph is stuck to a fixationmember or a mediating member. Therefore, the stress tends to remain,resulting from, for example, the curing and the shrinkage of an adhesiveand the heating treatment required for the sticking and the lamination.It is feared that the displacement action is disturbed by the internalresidual stress, and it is impossible to realize the displacement andthe resonance frequency as designed. Especially, when the actuator issmall in size, the influence of the adhesive is increased by itself.

[0012] Accordingly, a method is conceived in order to exclude theinfluence of the adhesive required to effect the sticking, in which theactuator is composed of, for example, an integrated sintered productmade of ceramics to give a structure in which no adhesive is used.However, also in this case, it is inevitably feared that the internalresidual stress arises due to the difference in behavior of thermalshrinkage between respective members during the sintering.

[0013] Further, when the actuator is small in size, a problem isinvolved such that the fixation property of the actuator and theattachment property of the actuator to another part are deficient.

SUMMARY OF THE INVENTION

[0014] The present invention has been made taking the foregoing problemsinto consideration, an object of which is to provide apiezoelectric/electrostrictive device and a method for producing thesame which make it possible to obtain a displacement element that isscarcely affected by harmful vibration and capable of high speedresponse with high mechanical strength while being excellent in handlingperformance, shock resistance, and moisture resistance, making itpossible to realize a light weight of the device, especially a lightweight of a movable section or a fixation section, and improve thehandling performance of the device and the attachment performance forparts to be attached to the movable section or the fixation performanceof the device, so that the movable section may be greatly displaced at arelatively low voltage, and it is possible to achieve a high speed ofthe displacement action of the device, especially of the movable section(realization of a high resonance frequency), as well as a sensor elementwhich makes it possible to accurately detect vibration of the movablesection.

[0015] According to the present invention, there is provided apiezoelectric/electrostrictive device comprising a pair of mutuallyopposing thin plate sections and a fixation section for supporting thethin plate sections; movable sections provided at forward end portionsof the pair of thin plate sections; and one or morepiezoelectric/electrostrictive elements arranged on at least one thinplate section of the pair of thin plate sections; wherein any one of themovable sections and the fixation section has mutually opposing endsurfaces; and a distance between the end surfaces is not less than alength of the movable section.

[0016] The movable section, the fixation section, and the thin platesection may be made of ceramics or metal. Alternatively, each of thecomponents may be made of a ceramic material, or each of them may bemade of a metal material. Further, each of the components may beconstructed to have a hybrid structure obtained by combining thoseproduced from materials of ceramics and metal.

[0017] It is also preferable that any one of the movable section and thefixation section is provided with a cutoff section; and a part of thecutoff section constitutes the mutually opposing end surfaces. It isalso preferable that the thin plate section, the movable section, andthe fixation section are composed of a ceramic substrate integrated intoone unit by co-firing a ceramic green laminate and cutting offunnecessary portions. It is also preferable that thepiezoelectric/electrostrictive element has a film-shaped configuration,and it is integrated with the ceramic substrate by means of sintering.

[0018] In this arrangement, the piezoelectric/electrostrictive elementmay have a piezoelectric/electrostrictive layer and a pair of electrodesformed on the piezoelectric/electrostrictive layer. It is alsopreferable that the piezoelectric/electrostrictive element has apiezoelectric/electrostrictive layer and a pair of electrodes formed onboth sides of the piezoelectric/electrostrictive layer, and oneelectrode of the pair of electrodes is formed on at least the thin platesection. In this arrangement, the vibration caused by thepiezoelectric/electrostrictive element can be efficiently transmittedvia the thin plate section to the movable section or the fixationsection. Thus, it is possible to improve the response performance.Especially, it is preferable that the piezoelectric/electrostrictiveelement is constructed in a stacked form comprising a plurality of unitseach including the piezoelectric/electrostrictive layer and the pair ofelectrodes.

[0019] When the arrangement as described above is adopted, the followingfeature is achieved. That is, the generated force of thepiezoelectric/electrostrictive element is increased, and thus it ispossible to obtain large displacement. Further, it is possible to obtaina high resonance frequency owing to the increase in rigidity of thedevice itself, making it easy to achieve the high speed of thedisplacement action.

[0020] It is also preferable that a gap is formed between the mutuallyopposing end surfaces. It is also preferable that a member which is thesame as a constitutive member of any one of the movable section and thefixation section, or a plurality of members which are differenttherefrom are interposed between the mutually opposing end surfaces, thesame member or the different members including, for example, glass,cement, and organic resin, preferably organic resin such as those basedon epoxy, acrylic, polyimide, phenol, silicone, terpene, xylene,styrene, melamine, methacrylic, and rubber, or mixture or copolymerthereof. Especially, in view of, for example, the joining performance,the handling performance, and the hardness, it is preferable to alloworganic resin or the like based on epoxy, acrylic, and methacrylic tointervene. In order to further enhance the hardness, it is alsopreferable to mix a filler such as an inorganic material.

[0021] Especially, it is possible to effectively realize a light weightof the movable section or the fixation section by forming the gapbetween the mutually opposing end surfaces, allowing the member lighterthan the constitutive member of the movable section or the fixationsection to intervene between the mutually opposing end surfaces, orjoining the end surfaces with small one of the members described above.Accordingly, it is possible to increase the resonance frequency withoutdecreasing the amount of displacement of the movable section or thefixation section.

[0022] When the gap is formed between the mutually opposing endsurfaces, a part of the movable section or the fixation sectionincluding one end surface and another part of the movable section or thefixation section including the other end surface are more flexible,resulting in strong resistance to the deformation. Therefore, it ispossible to obtain excellent handling performance of thepiezoelectric/electrostrictive device.

[0023] Further, the distance between the end surfaces is not less thanthe length of the movable section. Therefore, the attachment area can beincreased, when another part is attached to the movable section. Thus,it is possible to improve the attachment performance for the part. It isnow assumed that the part is secured, for example, with an adhesive orthe like. The part can be held by being interposed on the both sides.Thus, it is possible to reliably secure the part.

[0024] When the part is held by being interposed on the both sides, theheight of the part and the height of the movable section are not simplyadded. Accordingly, it is possible to maintain the height of the wholeincluding the part to be low. Further, the length of the movable sectioncan be made smaller than the distance on the side of the end surface.Therefore, the physical property of an adhesive or the like for stickingor bonding the part effectively makes the action. Thus, it is possibleto increase the displacement.

[0025] On the other hand, when the fixation section has the mutuallyopposing end surfaces, it is possible to strongly fix thepiezoelectric/electrostrictive device according to this invention to apredetermined fixation portion. Thus, it is possible to improve thereliability.

[0026] As described above, according to the present invention, it ispossible to obtain the displacement element which is scarcely affectedby harmful vibration and capable of high speed response with highmechanical strength while being excellent in handling performance, shockresistance, and moisture resistance, making it possible to realize alight weight of the device, especially a light weight of the movablesection or the fixation section, and improve the handling performance ofthe device as well as the attachment performance for parts to beattached to the movable section, the miniaturization, and the fixationperformance of the device, so that the movable section may be greatlydisplaced, and it is possible to achieve a high speed of thedisplacement action of the movable section (realization of a highresonance frequency), as well as the sensor element which makes itpossible to accurately detect vibration of the movable section.

[0027] In the production of the piezoelectric/electrostrictive device,for example, when the piezoelectric electrostrictive element is formedon a ceramic laminate (obtained by laminating ceramic green sheetsfollowed by sintering into one unit), for example, by means of thelamination or the integrated sintering based on the use of the filmformation method as described later on, the internal residual stress isgenerated at a portion to be formed into thepiezoelectric/electrostrictive element and/or the thin plate section.Especially, when the piezoelectric/electrostrictive element is formed onthe ceramic laminate by means of the integrated sintering, the internalresidual stress tends to be generated at the portion to be convertedinto the piezoelectric/electrostrictive element and/or the thin platesection, due to the shrinkage and the difference in coefficient ofthermal expansion of the constitutive members caused during thesintering.

[0028] If the piezoelectric/electrostrictive device is produced and usedstarting from this state, the movable section does not exhibit thedesired displacement in some cases, even when a predetermined electricfield is applied to the piezoelectric/electrostrictive layer forconstructing the piezoelectric/electrostrictive element, because of thefollowing reason. That is, the material characteristic of thepiezoelectric/electrostrictive layer and the displacement action of themovable section are inhibited by the internal residual stress generatedin the piezoelectric/electrostrictive element and/or the thin platesection.

[0029] In the present invention, the mutually opposing end surfaces areprovided on any one of the movable section and the fixation section.Therefore, the distance between the end surfaces is, for example,shortened by the internal residual stress generated in thepiezoelectric/electrostrictive element and/or the thin plate section.That is, the internal residual stress, which has been generated in thepiezoelectric/electrostrictive element and/or the thin plate section, isreleased by the movement of the end surfaces.

[0030] Further, in the present invention, the distance between the endsurfaces is made to be wide. Therefore, even when the distance betweenthe end surfaces is narrowed due to the internal residual stress, it ispossible to give a margin sufficient to attach another part between theend surfaces.

[0031] As described above, in the present invention, the displacementaction of the movable section is not inhibited by the internal residualstress. It is possible to obtain the displacement action of the movablesection as approximately designed and expected. Additionally, therelease of the internal residual stress also makes it possible toimprove the mechanical strength of the device.

[0032] When a hole is formed by both inner walls of the pair of thinplate sections, inner walls of the movable sections, inner walls of theplurality of members, and an inner wall of the fixation section, it isalso preferable that the hole is filled with a gel material. In thisarrangement, although the displacement action of the movable section isusually restricted due to the presence of the filler material, theinvention described above intends to reduce the weight as a result ofthe formation of the end surfaces on the movable section or the fixationsection, and increase the displacement amount of the movable section.Therefore, the restriction of the displacement action of the movablesection by the filler material is counteracted, and it is possible torealize the effect owing to the presence of the filler material, i.e.,the realization of the high resonance frequency and the maintenance ofthe rigidity.

[0033] According to another aspect of the present invention, there isprovided a method for producing a piezoelectric/electrostrictive devicecomprising a pair of mutually opposing thin plate sections and afixation section for supporting the thin plate sections; movablesections provided at forward end portions of the pair of thin platesections; and one or more piezoelectric/electrostrictive elementsarranged on at least one thin plate section of the pair of thin platesections; the method comprising a step of forming the movable sectionsor the fixation section having mutually opposing end surfaces wherein adistance between the end surfaces is not less than a length of themovable section, by cutting off a predetermined part of any one of aportion to be formed into the movable sections or a portion to be formedinto the fixation section after producing at least thepiezoelectric/electrostrictive element on the thin plate section.

[0034] As a result, there is provided the movable section or thefixation section which has the mutually opposing end surfaces.Accordingly, the internal residual stress, which has been generated inthe piezoelectric/electrostrictive element and/or the thin plate sectionduring the production, is released, for example, by shortening thedistance between the end surfaces. Therefore, the displacement action ofthe movable section is not inhibited by the internal residual stress.

[0035] The phrase “after producing the piezoelectric/electrostrictiveelement” referred to herein indicates a state in which at least thepiezoelectric/electrostrictive layer is formed. As for the electrode tobe formed after the formation of the piezoelectric/electrostrictivelayer, the electrode may be formed after performing the cutoff to formthe movable section or the fixation section having the mutually opposingend surfaces.

[0036] The provision of the movable section or the fixation sectionhaving the mutually opposing end surfaces realizes the light weight ofthe movable section or the fixation section. Therefore, thepiezoelectric/electrostrictive device, which makes it possible toincrease the resonance frequency, can be efficiently produced with easewithout decreasing the amount of displacement of the movable section.Thus, it is possible to realize the mass production of the highperformance piezoelectric/electrostrictive device.

[0037] Further, the movable section or the fixation section is bent moreflexibly, and it is strongly resistant to deformation. Therefore, thepiezoelectric/electrostrictive device is excellent in handlingperformance. Owing to the presence of the mutually opposing end surfacesand the wide distance between the end surfaces, when another part isattached to the movable section, it is possible to provide a largeattachment area therefor. Thus, it is possible to improve the attachmentperformance for the part. When a part is interposed and bonded, it ispossible to improve the displacement.

[0038] According to still another aspect of the present invention, thereis provided a method for producing a piezoelectric/electrostrictivedevice comprising a pair of mutually opposing thin plate sections and afixation section for supporting the thin plate sections; movablesections provided at forward end portions of the pair of thin platesections; and one or more piezoelectric/electrostrictive elementsarranged on at least one thin plate section of the pair of thin platesections; the method comprising a step of producing a ceramic laminateby integrally sintering a ceramic green laminate including at least aceramic green sheet having a window and ceramic green sheets to beformed into the thin plate sections thereafter to produce the ceramiclaminate; a step of forming the piezoelectric/electrostrictive elementon an outer surface of a portion of the ceramic laminate to be formedinto the thin plate section; and a cutoff step of forming the movablesections or the fixation section having at least mutually opposing endsurfaces wherein a distance between the end surfaces is not less than alength of the movable section, by means of at least one time of cutofftreatment for the ceramic laminate formed with thepiezoelectric/electrostrictive element.

[0039] Accordingly, in the production of thepiezoelectric/electrostrictive device, especially when thepiezoelectric/electrostrictive element is formed on the ceramic laminateby means of the sintering, the internal residual stress, which isgenerated in the piezoelectric/electrostrictive element and/or the thinplate section, can be effectively released. Therefore, when thepiezoelectric/electrostrictive device is produced by using the ceramicgreen sheet-laminating method, it is possible to realize the lightweight of the device, especially the light weight of the movable sectionor the fixation section, and improve the handling performance of thedevice, the attachment performance for parts to be attached to themovable section, and the fixation performance of the device. Thus, it ispossible to allow the movable section to make large displacement.

[0040] It is also preferable that in the step of producing the ceramiclaminate, the ceramic laminate is produced by integrally sintering aceramic green laminate including a plurality of ceramic green sheetseach having a window for forming the movable section or the fixationsection having at least the mutually opposing end surfaces, and theceramic green sheets to be formed into the thin plate sectionsthereafter to produce the ceramic laminate; and in the cutoff step, themovable section or the fixation section, which has at least the mutuallyopposing end surfaces and in which the distance between the end surfacesis not less than the length of the movable section, is formed by meansof the cutoff treatment for the ceramic laminate formed with thepiezoelectric/electrostrictive element.

[0041] It is also preferable that in the step of producing the ceramiclaminate, the ceramic laminate is produced by integrally sintering aceramic green laminate including a plurality of ceramic green sheetseach having a window for forming a portion to be formed into the movablesection or a portion to be formed into the fixation section having atleast the mutually opposing end surfaces partially connected to oneanother, and the ceramic green sheets to be formed into the thin platesections thereafter to produce the ceramic laminate; and in the cutoffstep, the portion to be formed into the movable section or the portionto be formed into the fixation section having at least the mutuallyopposing end surfaces partially connected to one another is formed bymeans of the cutoff treatment for the ceramic laminate formed with thepiezoelectric/electrostrictive element, and the movable section or thefixation section, which has the mutually opposing end surfaces and inwhich the distance between the end surfaces is not less than the lengthof the movable section, is formed by cutting off the connecting portion.

[0042] It is also preferable that the production method furthercomprises a step of allowing a plurality of members different from aconstitutive member of the movable section or the fixation section tointervene between the mutually opposing end surfaces. In this case,organic resin may be used as at least one member of the plurality ofmembers.

[0043] Therefore, the piezoelectric/electrostrictive device and themethod for producing the same according to the present invention canmake the use of the active device including, for example, varioustransducers, various actuators, frequency region functional parts(filters), transformers, vibrators, resonators, oscillators, anddiscriminators for the communication and the power generation, as wellas the sensor element for various sensors including, for example,ultrasonic sensors, acceleration sensors, angular velocity sensors,shock sensors, and mass sensors. Especially, thepiezoelectric/electrostrictive device and the method for producing thesame according to the present invention can be preferably utilized forvarious actuators to be used for the mechanism for adjusting thedisplacement and the positioning and for adjusting the angle for variousprecision parts such as those of optical instruments and precisionmechanical equipments.

[0044] The above and other objects, features, and advantages of thepresent invention will become more apparent from the followingdescription when taken in conjunction with the accompanying drawings inwhich a preferred embodiment of the present invention is shown by way ofillustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

[0045]FIG. 1 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to an embodiment of thepresent invention;

[0046]FIG. 2 shows a magnified view illustrating a first modifiedembodiment of the piezoelectric/electrostrictive element;

[0047]FIG. 3 shows a magnified view illustrating a second modifiedembodiment of the piezoelectric/electrostrictive element;

[0048]FIG. 4 shows a perspective view illustrating, with partialomission, a third modified embodiment of thepiezoelectric/electrostrictive element;

[0049]FIG. 5 shows a perspective view illustrating, with partialomission, a fourth modified embodiment of thepiezoelectric/electrostrictive element;

[0050]FIG. 6 shows a perspective view illustrating a first modifiedembodiment of the piezoelectric/electrostrictive device according to theembodiment of the present invention;

[0051]FIG. 7 shows a perspective view illustrating a second modifiedembodiment of the piezoelectric/electrostrictive device according to theembodiment of the present invention;

[0052]FIG. 8 illustrates a situation in which both of thepiezoelectric/electrostrictive elements do not make the displacementaction in the piezoelectric/electrostrictive device according to thesecond modified embodiment;

[0053]FIG. 9A shows a waveform illustrating a voltage waveform to beapplied to the first piezoelectric/electrostrictive element;

[0054]FIG. 9B shows a waveform illustrating a voltage waveform to beapplied to the second piezoelectric/electrostrictive element;

[0055]FIG. 10 illustrates a situation in which thepiezoelectric/electrostrictive element makes the displacement action inthe piezoelectric/electrostrictive device according to the secondmodified embodiment;

[0056]FIG. 11 shows a perspective view illustrating a third modifiedembodiment of the piezoelectric/electrostrictive device according to theembodiment of the present invention;

[0057]FIG. 12 shows a perspective view illustrating a fourth modifiedembodiment of the piezoelectric/electrostrictive device according to theembodiment of the present invention;

[0058]FIG. 13 shows a perspective view illustrating a fifth modifiedembodiment of the piezoelectric/electrostrictive device;

[0059]FIG. 14 shows a perspective view illustrating a sixth modifiedembodiment of the piezoelectric/electrostrictive device;

[0060]FIG. 15 shows a perspective view illustrating a seventh modifiedembodiment of the piezoelectric/electrostrictive device;

[0061]FIG. 16 illustrates a process for laminating ceramic green sheetsrequired for a first production method;

[0062]FIG. 17 illustrates a state in the first production method inwhich a ceramic green laminate is formed;

[0063]FIG. 18 illustrates a state in the first production method inwhich the ceramic green laminate is converted into a sintered ceramiclaminate, and then a piezoelectric/electrostrictive element is formed onthe ceramic laminate;

[0064]FIG. 19 illustrates an intermediate process in the firstproduction method in which the ceramic laminate is cut alongpredetermined cutting lines to provide thepiezoelectric/electrostrictive device according to the embodiment of thepresent invention;

[0065]FIG. 20A illustrates a state in which the internal residual stressis generated in the thin plate section and thepiezoelectric/electrostrictive layer;

[0066]FIG. 20B illustrates a state in which a central portion of amovable section is cut off;

[0067]FIG. 21 illustrates a process for laminating ceramic green sheetsrequired for a second production method;

[0068]FIG. 22 illustrates a state in the second production method inwhich a ceramic green laminate is formed;

[0069]FIG. 23 illustrates a state in the second production method inwhich the ceramic green laminate is converted into a sintered ceramiclaminate, and then a piezoelectric/electrostrictive element is formed onthe ceramic laminate;

[0070]FIG. 24 illustrates a state in the second production method inwhich the ceramic laminate is cut along predetermined cutting lines toprovide the piezoelectric/electrostrictive device according to theembodiment of the present invention;

[0071]FIG. 25 illustrates a process for laminating ceramic green sheetsrequired for a third production method;

[0072]FIG. 26 illustrates a state in the third production method inwhich a ceramic green laminate is formed;

[0073]FIG. 27 illustrates a state in the third production method inwhich the ceramic green laminate is converted into a sintered ceramiclaminate, and then a piezoelectric/electrostrictive element is formed onthe ceramic laminate;

[0074]FIG. 28 illustrates an intermediate process in the thirdproduction method in which the ceramic laminate is cut alongpredetermined cutting lines to provide thepiezoelectric/electrostrictive device according to the embodiment of thepresent invention;

[0075]FIG. 29 illustrates a process for laminating ceramic green sheetsrequired for a fourth production method;

[0076]FIG. 30 illustrates a state in the fourth production method inwhich a ceramic green laminate is formed;

[0077]FIG. 31 illustrates a state in the fourth production method inwhich the ceramic green laminate is converted into a sintered ceramiclaminate, and then a piezoelectric/electrostrictive element is formed onthe ceramic laminate;

[0078]FIG. 32 illustrates an intermediate process in the fourthproduction method in which the ceramic laminate is cut alongpredetermined cutting lines to provide thepiezoelectric/electrostrictive device according to the embodiment of thepresent invention;

[0079]FIG. 33 illustrates a process for laminating ceramic green sheetsrequired for a fifth production method;

[0080]FIG. 34 illustrates a state in the fifth production method inwhich a ceramic green laminate is formed;

[0081]FIG. 35 illustrates a state in the fifth production method inwhich the ceramic green laminate is sintered into a ceramic laminate;

[0082]FIG. 36 illustrates a state in the fifth production method inwhich piezoelectric/electrostrictive elements, which are constructed asseparate members, are bonded to surfaces of metal plates to serve asthin plate sections respectively;

[0083]FIG. 37 illustrates a state in the fifth production method inwhich the metal plate is bonded to the ceramic laminate to provide ahybrid laminate;

[0084]FIG. 38 illustrates a state in the fifth production method inwhich the hybrid laminate is cut along predetermined cutting lines toprovide a piezoelectric/electrostrictive device according to an eighthmodified embodiment;

[0085]FIG. 39 illustrates a state in a sixth production method in whicha ceramic green laminate is sintered into a ceramic laminate, and then ahole is filled with a filler material;

[0086]FIG. 40 illustrates a state in the sixth production method inwhich the metal plates to serve as thin plate sections respectively arebonded to the ceramic laminate to provide a hybrid laminate; and

[0087]FIG. 41 shows an arrangement of a piezoelectric/electrostrictivedevice concerning an illustrative conventional technique.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0088] Explanation will be made below with reference to FIGS. 1 to 40for illustrative embodiments of the piezoelectric/electrostrictivedevice and the production method for the same according to the presentinvention.

[0089] It is noted that the piezoelectric/electrostrictive deviceresides in a concept which includes the element for mutually convertingthe electric energy and the mechanical energy by the aid of thepiezoelectric/electrostrictive element. Therefore, thepiezoelectric/electrostrictive device is most preferably used as theactive element such as various actuators and vibrators, especially asthe displacement element based on the use of the displacement broughtabout by the inverse piezoelectric effect and the electrostrictiveeffect. Additionally, the piezoelectric/electrostrictive device is alsopreferably used as the passive element such as acceleration sensorelements and shock sensor elements.

[0090] As shown in FIG. 1, the piezoelectric/electrostrictive device 10according to this embodiment is provided with a substrate 16 whichcomprises, in an integrated manner, a pair of mutually opposing thinplate sections 12 a, 12 b, and a fixation section 14 for supporting thethin plate sections 12 a, 12 b. The piezoelectric/electrostrictivedevice 10 comprises piezoelectric/electrostrictive elements 18 a, 18 bwhich are formed at respective parts of the pair of thin plate sections12 a, 12 b respectively.

[0091] In other words, the piezoelectric/electrostrictive device 10 isconstructed such that the pair of thin plate sections 12 a, 12 b aredisplaced in accordance with the driving of thepiezoelectric/electrostrictive element or elements 18 a and/or 18 b, orthe displacement of the thin plate sections 12 a, 12 b is detected bythe piezoelectric/electrostrictive element or elements 18 a and/or 18 b.Therefore, in the embodiment shown in FIG. 1, actuator sections 19 a, 19b are constructed by the thin plate sections 12 a, 12 b and thepiezoelectric/electrostrictive elements 18 a, 18 b.

[0092] Further, respective forward end portions of the pair of thinplate sections 12 a, 12 b are thick-walled toward the inside. Thethick-walled portions function as movable sections 20 a, 20 b which aredisplaced in accordance with the displacement action of the thin platesections 12 a, 12 b.

[0093] The forward end portions of the pair of thin plate sections 12 a,12 b will be hereinafter referred to as “movable sections 20 a, 20 b”.

[0094] Those usable as the substrate 16 include a structure comprisingceramics or metal as a whole, and a hybrid structure obtained bycombining products produced with materials of ceramics and metal.

[0095] Those adoptable for the substrate 16 include, for example, astructure in which respective parts are bonded to one another with anadhesive such as organic resin or glass or the like, a ceramicintegrated structure which is obtained by sintering and integrating aceramic green laminate into one unit, and a metal integrated structureintegrated, for example, by brazing, soldering, eutectic bonding, orwelding into one unit. Preferably, it is desirable to construct thesubstrate 16 with a ceramic laminate integrated into one unit bysintering a ceramic green laminate.

[0096] The time-dependent change of state scarcely occurs in theintegrated product of ceramic, because no adhesive exists at joinedportions between the respective parts. Therefore, the reliability of thejoined portion is high, giving a structure which is advantageous toensure the rigidity. Additionally, the integrated product of ceramic canbe produced with ease by means of the method for laminating ceramicgreen sheets as described later on.

[0097] The piezoelectric/electrostrictive elements 18 a, 18 b areprepared as separate members as described later on, and the preparedpiezoelectric/electrostrictive elements 18 a, 18 b are stuck to thesubstrate 16 with an adhesive such as organic resin or glass or by meansof, for example, brazing, soldering, or eutectic bonding. Alternatively,the piezoelectric/electrostrictive elements 18 a, 18 b are directlyformed on the substrate 16 by using the film formation method not byusing the sticking method described above.

[0098] The piezoelectric/electrostrictive element 18 a, 18 b comprises apiezoelectric/electrostrictive layer 22, and a pair of electrodes 24, 26which are formed on both sides of the piezoelectric/electrostrictivelayer 22. The first electrode 24 of the pair of electrodes 24, 26 isformed at least on the pair of thin plate sections 12 a, 12 b.

[0099] In the embodiment of the present invention, explanation will bemade principally for a case in which each of thepiezoelectric/electrostrictive layer 22 and the pair of electrodes 24,26 has a multilayered structure, the first electrode 24 and the secondelectrode 26 are alternately stacked with each other to give asubstantially comb-shaped cross section, and thus thepiezoelectric/electrostrictive element 18 a, 18 b is provided, which hasa multiple stage structure at a portion at which the first electrodes 24and the second electrodes 26 are overlapped with each other with thepiezoelectric/electrostrictive layer 22 interposed therebetween.However, there is no limitation to the multilayered structure. Asingle-layered structure may be available. In this embodiment, thenumber of the multiple layers is not specifically limited. However, itis preferable to use not more than ten layers, and more preferably notmore than five layers.

[0100]FIG. 1 is illustrative of a case in which thepiezoelectric/electrostrictive layer 22 has a three-layered structure,the first electrode 24 is formed to have a comb-shaped configuration tobe located at the lower surface of the first layer (side surface of thethin plate section 12 a, 12 b) and at the upper surface of the secondlayer, and the second electrode 26 is formed to have a comb-shapedconfiguration to be located at the upper surface of the first layer andat the upper surface of the third layer. In the case of thisarrangement, the number of terminals 28, 30, can be decreased bymutually connecting the first electrodes 24 and the second electrodes 26respectively to be common. Therefore, the increase in size, which wouldbe otherwise caused by the multilayered structure of thepiezoelectric/electrostrictive element 18 a, 18 b, can be suppressed.

[0101] The voltage is applied to the pair of electrodes 24, 26 viaterminals (pads) 28, 30 of the respective electrodes 24, 26 formed onthe both side surfaces (element formation surfaces) of the fixationsection 14 respectively. The respective terminals 28, 30 are positionedas follows. That is, the terminal 28 corresponding to the firstelectrode 24 is formed at the position deviated toward the rearward endof the fixation section 14. The terminal 30 corresponding to the secondelectrode 26 disposed on the side of the external space is formed at theposition deviated toward the inner wall of the fixation section 14.

[0102] In this embodiment, the piezoelectric/electrostrictive device 10can be individually fixed by utilizing the surfaces respectivelydifferent from the surfaces on which the terminals 28, 30 are arranged.As a result, it is possible to obtain the high reliability for both ofthe fixation of the piezoelectric/electrostrictive device 10 and theelectric connection between the circuit and the terminals 28, 30. Inthis arrangement, the electric connection between the terminals 28, 30and the circuit is made, for example, by means of the flexible printedcircuit (also referred to as FPC), the flexible flat cable (alsoreferred to as FFC), and the wire bonding.

[0103] When the piezoelectric/electrostrictive element 18 a, 18 b havingthe multilayered structure is used as described above, then the drivingforce of the actuator section 19 a, 19 b is increased, and thus it ispossible to contemplate the large displacement. Further, the rigidity ofthe piezoelectric/electrostrictive device 10 itself is increased, andthus it is possible to realize the high resonance frequency, making iteasy to achieve the realization of a high speed of the displacementaction.

[0104] When the number of stages is increased, it is possible toincrease the driving force of the actuator sections 19 a, 19 b. However,the electric power consumption is also increased in accordancetherewith. Therefore, when the device is practically produced and used,for example, it is preferable that the number of stages is appropriatelydetermined depending on the way of use and the state of use.

[0105] In the case of the piezoelectric/electrostrictive device 10according to this embodiment, even when the driving force of theactuator section 19 a, 19 b is increased by using thepiezoelectric/electrostrictive element 18 a, 18 b, the width of the thinplate section 12 a, 12 b (distance in the Y axis direction) is basicallyunchanged. Therefore, the device is extremely preferred to makeapplication, for example, to the actuator for the purpose of the ringingcontrol and the positioning of the magnetic head for the hard disk to beused in an extremely narrow gap.

[0106] Another example of the piezoelectric/electrostrictive element 18a, 18 b is preferably shown, for example, in FIG. 2. That is, thepiezoelectric/electrostrictive layer 22 has a five-layered structure.The first electrode 24 is formed to have a comb-shaped configuration tobe located at the upper surface of the first layer, the upper surface ofthe third layer, and the upper surface of the fifth layer. The secondelectrode 26 is formed to have a comb-shaped configuration to be locatedat the upper surface of the second layer and the upper surface of thefourth layer.

[0107] Still another example is also available as shown in FIG. 3. Thatis, the piezoelectric/electrostrictive layer 22 is allowed to have afive-layered structure as well. The first electrode 24 is formed to havea comb-shaped configuration to be located at the upper surface of thefirst layer, the upper surface of the third layer, and the upper surfaceof the fifth layer. The second electrode 26 is formed to have acomb-shaped configuration to be located at the lower surface of thefirst layer, the upper surface of the second layer, and the uppersurface of the fourth layer.

[0108] The voltage is applied to the pair of electrodes 24, 26 via ends(hereinafter referred to as “terminal sections 24 a, 26 a) of therespective electrodes 24, 26 formed on the fifth layer of thepiezoelectric/electrostrictive layer 22. The respective terminalsections 24 a, 26 a are formed and separated from each other in such adegree that they can be electrically insulated from each other.

[0109] The piezoelectric/electrostrictive element 18 a, 18 b describedabove is illustrative of the case of the construction of the so-calledsandwich structure in which the piezoelectric/electrostrictive layer 22is allowed to intervene between the pair of electrodes 24, 26.

[0110] Alternatively, as shown in FIG. 4, a pair of comb-shapedelectrodes 24, 26 may be formed on the first principal surface of thepiezoelectric/electrostrictive layer 22 formed on at least the sidesurface of the thin plate section 12 a, 12 b. Further alternatively, asshown in FIG. 5, a pair of comb-shaped electrodes 24, 26 are formed andembedded in the piezoelectric/electrostrictive layer 22 formed on atleast the side surface of the thin plate section 12 a, 12 b.

[0111] The structure shown in FIG. 4 is advantageous in that it ispossible to suppress the electric power consumption to be low. Thestructure shown in FIG. 5 makes it possible to effectively utilize theinverse piezoelectric effect in the direction of the electric fieldhaving large generated force and strain, which is advantageous to causethe large displacement.

[0112] Specifically, the piezoelectric/electrostrictive element 18 a, 18b shown in FIG. 4 comprises the pair of electrodes 24, 26 having thecomb-shaped structure formed on the first principal surface of thepiezoelectric/electrostrictive layer 22. In this structure, the firstelectrode 24 and the second electrode 26 are mutually opposed to oneanother in an alternate manner with a gap 32 having a constant widthinterposed therebetween. FIG. 4 is illustrative of the case in which thepair of electrodes 24, 26 are formed on the first principal surface ofthe piezoelectric/electrostrictive layer 22. Alternatively, the pair ofelectrodes 24, 26 may be formed between the thin plate section 12 a, 12b and the piezoelectric/electrostrictive layer 22. Furtheralternatively, the pair of comb-shaped electrodes 24, 26 may be formedon the first principal surface of the piezoelectric/electrostrictivelayer 22 and between the thin plate section 12 a, 12 b and thepiezoelectric/electrostrictive layer 22 respectively.

[0113] On the other hand, in the piezoelectric/electrostrictive element18 a, 18 b shown in FIG. 5, the pair of electrodes 24, 26 having thecomb-shaped structure are formed so that they are embedded in thepiezoelectric/electrostrictive layer 22. In this structure, the firstelectrode 24 and the second electrode 26 are mutually opposed to oneanother in an alternate manner with a gap 32 having a constant widthinterposed therebetween.

[0114] The piezoelectric/electrostrictive elements 18 a, 18 b as shownin FIGS. 4 and 5 can be preferably used for thepiezoelectric/electrostrictive device 10 according to the embodiment ofthe present invention as well. When the pair of comb-shaped electrodes24, 26 are used as in the piezoelectric/electrostrictive elements 18 a,18 b shown in FIGS. 4 and 5, the displacement of thepiezoelectric/electrostrictive element 18 a, 18 b can be increased bydecreasing the pitch D of the comb teeth of the respective electrodes24, 26.

[0115] The distance Lc between the mutually opposing end surfaces 34 a,34 b of the movable sections 20 a, 20 b is not less than the length ofthe movable section 20 a, 20 b (correctly the length of the movablesection 20 a, 20 b in the Z axis direction) Df. For example, as shown inFIG. 1, a gap (air) 36 may be allowed to intervene between the endsurfaces 34 a, 34 b. Alternatively, as in piezoelectric/electrostrictivedevices 10 a, 10 b according to first and second modified embodimentsshown in FIGS. 6 and 7, a plurality of members, which are composed ofthe same material as that of the constitutive member of the movablesection 20 a, 20 b or which are composed of a material differenttherefrom, may be allowed to intervene between the end surfaces 34 a, 34b. In this arrangement, the mutually opposing end surfaces 34 a, 34 b ofthe respective movable sections 20 a, 20 b function as attachmentsurfaces 34 a, 34 b.

[0116] The piezoelectric/electrostrictive device 10 a according to thefirst modified embodiment shown in FIG. 6 is illustrative of thefollowing case. That is, the distance Lc between the attachment surfaces34 a, 34 b is set to be about 1.5-fold the length Df of the movablesection 20 a, 20 b. Further, three spacer members 37A, 37B, 37C, each ofwhich has a substantially identical thickness, are allowed to intervenebetween the attachment surfaces 34 a, 34 b.

[0117] The piezoelectric/electrostrictive device 10 b according to thesecond modified embodiment shown in FIG. 7 is illustrative of thefollowing case. That is, the distance Lc between the attachment surfaces34 a, 34 b is set to be about 1.5-fold the length Df of the movablesection 20 a, 20 b. Further, one large spacer member 37 is bondedbetween the attachment surfaces 34 a, 34 b by the aid of an adhesive 38.

[0118] Further, for example, in the piezoelectric/electrostrictivedevice 10 b according to the second modified embodiment, as shown inFIG. 8, for example, it is preferable that distances La, Lb from thecentral axis n of the spacer member 37 to the respective end surfaces 34a, 34 b are approximately identical to one another. In thepiezoelectric/electrostrictive devices 10 a, 10 b according to the firstand second modified embodiments, each of the three spacer members 37A to37C (see FIG. 6) and the spacer member 37 (see FIG. 7) has asubstantially rectangular parallelepiped-shaped configuration. Each ofthe side surfaces (surfaces opposed to the movable sections 20 a, 20 bof the thin plate sections 12 a, 12 b) is set to have the areal sizewhich is substantially the same as the areal size of each of theattachment surfaces 34 a, 34 b of the movable sections 20 a, 20 b of thethin plate sections 12 a, 12 b.

[0119] The operation of the piezoelectric/electrostrictive device 10 baccording to the second modified embodiment will now be explained by wayof example. At first, for example, when the twopiezoelectric/electrostrictive elements 18 a, 18 b are in the naturalstate, namely when both of the piezoelectric/electrostrictive elements18 a, 18 b do not make the displacement action, then the major axis m ofthe piezoelectric/electrostrictive device 10 b (major axis of thefixation section 14) is substantially coincident with the central axis nof the spacer member 37 as shown in FIG. 8.

[0120] Starting from this state, for example, a sine wave Wa, which hasa predetermined bias electric potential Vb, is applied to the pair ofelectrodes 24, 26 of the first piezoelectric/electrostrictive element 18a as shown in a waveform figure shown in FIG. 9A, while a sine wave Wb,which has a phase different from that of the sine wave Wa by about 1800,is applied to the pair of electrodes 24, 26 of the secondpiezoelectric/electrostrictive element 18 b as shown in FIG. 9B.

[0121] The piezoelectric/electrostrictive layer 22 of the firstpiezoelectric/electrostrictive element 18 a makes the contractiondisplacement in the direction of the first principal surface at a stageat which, for example, a voltage having a maximum value is applied tothe pair of electrodes 24, 26 of the firstpiezoelectric/electrostrictive element 18 a. Accordingly, as shown inFIG. 10, for example, the stress is generated for the first thin platesection 12 a to bend the thin plate section 12 a, for example, in therightward direction as shown by the arrow A. Therefore, the first thinplate section 12 a is bent in the rightward direction. At this time, astate is given, in which no voltage is applied to the pair of electrodes24, 26 of the second piezoelectric/electrostrictive element 18 b.Therefore, the second thin plate section 12 b follows the bending of thefirst thin plate section 12 a, and it is bent in the rightwarddirection. As a result, the movable sections 20 a, 20 b and the spacermember 37 are displaced, for example, in the rightward direction withrespect to the major axis m of the piezoelectric/electrostrictive device10 b. The displacement amount is changed depending on the maximum valueof the voltage applied to each of the piezoelectric/electrostrictiveelements 18 a, 18 b. For example, the larger the maximum value is, thelarger the displacement amount is.

[0122] Especially, when a material having a high coercive electric fieldis applied as the constitutive material for thepiezoelectric/electrostrictive layer 22, it is also preferable that thebias electric potential is adjusted so that the level of the minimumvalue is a slightly negative level as depicted by waveforms indicated bydashed lines in FIGS. 9A and 9B. In this case, for example, the stress,which is in the same direction as the bending direction of the firstthin plate section 12 a, is generated in the second thin plate section12 b by driving the piezoelectric/electrostrictive element (for example,the second piezoelectric/electrostrictive element 18 b) to which thenegative level is applied. Accordingly, it is possible to furtherincrease the displacement amount of the movable sections 20 a, 20 b andthe spacer member 37. In other words, when the waveforms indicated bythe dashed lines in FIGS. 9A and 9B are used, the device is allowed tohave such a function that the piezoelectric/electrostrictive element 18b or 18 a, to which the negative level is applied, supports thepiezoelectric/electrostrictive element 18 a or 18 b which principallymakes the displacement action.

[0123] As described above, in the piezoelectric/electrostrictive device10 according to the embodiment of the present invention, the minutedisplacement of the piezoelectric/electrostrictive element 18 a, 18 b isamplified into the large displacement action by utilizing the bending ofthe thin plate section 12 a, 12 b, and it is transmitted to the movablesections 20 a, 20 b. Accordingly, it is possible to greatly displace themovable sections 20 a, 20 b with respect to the major axis m of thepiezoelectric/electrostrictive device 10 b.

[0124] Especially, in this embodiment, the movable sections 20 a, 20 bare provided with the mutually opposing attachment surfaces 34 a, 34 b.In this arrangement, the space between the mutually opposing attachmentsurfaces 34 a, 34 b is the gap 36. Alternatively, the member, which islighter than the constitutive member of the movable sections 20 a, 20 b,is allowed to intervene between the mutually opposing attachmentsurfaces 34 a, 34 b. Thus, it is possible to effectively realize thelight weight of the movable sections 20 a, 20 b. It is possible toincrease the resonance frequency without decreasing the displacementamount of the movable sections 20 a, 20 b.

[0125] The frequency herein indicates the frequency of the voltagewaveform obtained when the movable sections 20 a, 20 b are displacedrightwardly and leftwardly by alternately switching the voltage appliedto the pair of electrodes 24, 26. The resonance frequency indicates themaximum frequency at which the displacement action of the movablesections 20 a, 20 b can follow in a predetermined vibration mode.

[0126] In the piezoelectric/electrostrictive device 10 according to thisembodiment, the movable sections 20 a, 20 b, the thin plate sections 12a, 12 b, and the fixation section 14 are integrated into one unit. It isunnecessary that all of the parts are formed with thepiezoelectric/electrostrictive material which is a fragile materialhaving a relatively heavy weight. Therefore, the device has thefollowing advantages. That is, the device has the high mechanicalstrength, and it is excellent in handling performance, shock resistance,and moisture resistance. Further, the operation of the device isscarcely affected by harmful vibration (for example, noise vibration andremaining vibration during high speed operation).

[0127] In this embodiment, when the space between the mutually opposingattachment surfaces 34 a, 34 b is the gap 36, the movable section 20 aincluding the first attachment surface 34 a and the movable section 20 bincluding the second attachment surface 34 b are easily bent, and thedevice is highly resistant to the deformation. Therefore, thepiezoelectric/electrostrictive device 10 is excellent in handlingperformance.

[0128] Owing to the presence of the mutually opposing attachmentsurfaces 34 a, 34 b, the surface area of the movable sections 20 a, 20 bis increased. Therefore, when another part is attached to the movablesection 20 a, 20 b, it is possible to increase the attachment area.Thus, it is possible to improve the attachment performance for the part.For example, if it is assumed that the part is secured with an adhesiveor the like, the part is bonded by the aid of not only the principalsurface of the movable section 20 a, 20 b (front surface and/or backsurface) but also the mutually opposing attachment surfaces 34 a, 34 b.It is possible to secure the part in a reliable manner.

[0129] In this embodiment, the piezoelectric/electrostrictive element 18a, 18 b is constructed to have the piezoelectric/electrostrictive layer22 and the pair of electrodes 24, 26 formed on the both sides of thepiezoelectric/electrostrictive layer 22. The first electrode 24 of thepair of electrodes 24, 26 is directly formed on at least the sidesurface of the thin plate section 12 a, 12 b. Therefore, the vibrationcaused by the piezoelectric/electrostrictive element 18 a, 18 b can beefficiently transmitted to the movable section 20 a, 20 b via the thinplate section 12 a, 12 b. Thus, it is possible to improve the responseperformance.

[0130] In this embodiment, as shown in FIG. 1, for example, the portion(substantial driving portion 40), at which the pair of electrodes 24, 26are overlapped with each other with the piezoelectric/electrostrictivelayer 22 interposed therebetween, is continuously formed over the rangefrom the part of the fixation section 14 to the part of the thin platesection 12 a, 12 b. If the substantial driving portion 40 is formed tofurther extend over a part of the movable section 20 a, 20 b, then it isfeared that the displacement action of the movable section 20 a, 20 b isinconsistent with the deformation of the substantial driving portion 40and the deformation of the thin plate section 12 a, 12 b, and it isimpossible to obtain the large displacement. However, in thisembodiment, the substantial driving portion 40 is formed such that itdoes not range over both of the movable section 20 a, 20 b and thefixation section 14. Therefore, it is possible to avoid theinconvenience of the restriction of the displacement action of themovable section 20 a, 20 b, and it is possible to increase thedisplacement amount of the movable section 20 a, 20 b.

[0131] On the other hand, when the piezoelectric/electrostrictiveelement 18 a, 18 b is formed on the part of the movable section 20 a, 20b, it is preferable that the substantial driving portion 40 is locatedover the range from the part of the movable section 20 a, 20 b to thepart of the thin plate section 12 a, 12 b, because of the followingreason. That is, if the substantial driving portion 40 is formed toextend up to a part of the fixation section 14, the displacement actionof the movable section 20 a, 20 b is restricted as described above.

[0132] The embodiment described above is illustrative of the case inwhich the attachment surfaces 34 a, 34 b are provided for the movablesections 20 a, 20 b. Alternatively, as in apiezoelectric/electrostrictive device 10 c according to a third modifiedembodiment shown in FIG. 11, end surfaces 34 a, 34 b may be provided forthe fixation section 14. In this case, for example, the movable sections20 a, 20 b, which are provided at the forward end portions of the pairof thin plate sections 12 a, 12 b, have an integrally connectedconfiguration. The mutually opposing end surfaces 34 a, 34 b areprovided for the fixation section 14.

[0133] Accordingly, in addition to the effect obtained when the mutuallyopposing attachment surfaces 34 a, 34 b are provided for the movablesections 20 a, 20 b as described above, thepiezoelectric/electrostrictive device 10 c according to the thirdmodified embodiment can be tightly fixed to a predetermined fixationportion. Thus, it is possible to improve the reliability. The length ofthe substantial driving portion 40 is preferably 20% to 95% of thelength of the thin plate section 12 a, 12 b, and more preferably 40% to80% thereof.

[0134] Next, explanation will be made for preferred illustrativeconstructions of the piezoelectric/electrostrictive device 10 accordingto the embodiment of the present invention.

[0135] At first, in order to ensure the displacement action of themovable section 20 a, 20 b, it is preferable that the distance Dg, bywhich the substantial driving portion 40 of thepiezoelectric/electrostrictive element 18 a, 18 b is overlapped with thefixation section 14 or the movable section 20 a, 20 b, is not less than½ of the thickness Dd of the thin plate section 12 a, 12 b.

[0136] The device is constructed such that the ratio Da/Db between thedistance (distance in the X axis direction) Da between the inner wallsof the thin plate sections 12 a, 12 b and the width (distance in the Yaxis direction) Db of the thin plate section 12 a, 12 b is 0.5 to 20.The ratio Da/Db is preferably 1 to 15 and more preferably 1 to 10. Theprescribed value of the ratio Da/Db is prescribed on the basis of thediscovery that the displacement amount of the movable section 20 a, 20 bcan be increased, and the displacement in the X-Z plane can bedominantly obtained.

[0137] On the other hand, it is desirable that the ratio De/Da betweenthe length (distance in the Z axis direction) De of the thin platesection 12 a, 12 b and the distance Da between the inner walls of thethin plate sections 12 a, 12 b is preferably 0.5 to 10 and morepreferably 0.5 to 5. The prescribed value of the ratio De/Da isprescribed on the basis of the discovery that the displacement amount ofthe movable sections 20 a, 20 b with the spacer members (37A to 37C or37) intervening therebetween can be increased, and the displacementaction can be performed at a high resonance frequency (high responsespeed can be achieved).

[0138] Therefore, in order to suppress the flapping displacement in theY axis direction or the vibration of the piezoelectric/electrostrictivedevice 10 according to this embodiment and provide the structure inwhich the high speed response performance is excellent and the largedisplacement is simultaneously obtained at a relatively low voltage, itis preferable that the ratio Da/Db is 0.5 to 20 and the ratio De/Da is0.5 to 10, and it is more preferable that the ratio Da/Db is 1 to 10 andthe ratio De/Da is 0.5 to 5.

[0139] Further, for example, in the case of thepiezoelectric/electrostrictive device 10 b according to the secondembodiment, the hole 42 is formed by the both inner walls of the pair ofthin plate sections 12 a, 12 b, the inner walls of the movable sections20 a, 20 b, and the inner wall of the spacer member 37 (and the innerwall of the adhesive 38), and the inner wall of the fixation section 14.It is preferable that the hole 42 is filled with a gel material, forexample, silicone gel. Usually, the displacement action of the movablesection 20 a, 20 b is restricted by the presence of such a fillermaterial. However, in the second modified embodiment, it is intended torealize the light weight brought about by the formation of the endsurface 34 a, 34 b for the movable section 20 a, 20 b and increase thedisplacement amount of the movable section 20 a, 20 b. Therefore, therestriction of the displacement action of the movable section 20 a, 20 bdue to the filler material is counteracted. Accordingly, it is possibleto realize the effect owing to the presence of the filler material,namely the realization of the high resonance frequency and themaintenance of the rigidity.

[0140] It is preferable that the length (distance in the Z axisdirection) Df of the movable section 20 a, 20 b is short, because of thefollowing reason. That is, it is possible to realize the light weightand increase the resonance frequency by shortening the length. Further,when an article is interposed, it is possible to improve thedisplacement. However, in order to ensure the rigidity of the movablesection 20 a, 20 b in the X axis direction and obtain its reliabledisplacement, it is desirable that the ratio Df/Dd with respect to thethickness Dd of the thin plate section 12 a, 12 b is not less than 2 andpreferably not less than 5.

[0141] The actual size of each component is determined considering, forexample, the joining area for attaching the part to the movable section20 a, 20 b, the joining area for attaching the fixation section 14 toanother member, the joining area for attaching the electrode terminal orthe like, and the strength, the durability, the necessary displacementamount, the resonance frequency, and the driving voltage of the entirepiezoelectric/electrostrictive device 10.

[0142] Specifically, for example, the distance Da between the innerwalls of the thin plate sections 12 a, 12 b is preferably 100 μm to 2000μm and more preferably 200 μm to 1600 μm. The width Db of the thin platesection 12 a, 12 b is preferably 50 μm to 2000 μm and more preferably100 μm to 500 μm. The thickness Dd of the thin plate section 12 a, 12 bis preferably 2 μm to 100 μm and more preferably 10 μm to 80 μm, whileit satisfies Db>Dd in relation to the width Db of the thin plate section12 a, 12 b, in order to make it possible to effectively suppress theflapping displacement which is the displacement component in the Y axisdirection. The length De of the thin plate section 12 a, 12 b ispreferably 200 μm to 3000 μm and more preferably 300 μm to 2000 μm. Thelength Df of the movable section 20 a, 20 b is preferably 50 μm to 2000μm, more preferably 100 μm to 1000 μm and especially preferably 200 μmto 600 μm.

[0143] The arrangement as described above exhibits such an extremelyexcellent effect that the displacement in the Y axis direction does notexceeds 10% with respect to the displacement in the X axis direction,while-the device can be driven at a low voltage by appropriately makingadjustment within the range of the size ratio and the actual size, andit is possible to suppress the displacement component in the Y axisdirection to be not more than 5%. In other words, the movable section 20a, 20 b is displaced in one axis direction, i.e., substantially in the Xaxis direction. Further, the high speed response is excellent, and it ispossible to obtain the large displacement at a relatively low voltage.

[0144] In the piezoelectric/electrostrictive device 10, the shape of thedevice is not the plate-shaped configuration (the thickness in thedirection perpendicular to the displacement direction is small) unlikeconventional one. Each of the movable section 20 a, 20 b and thefixation section 14 has the rectangular parallelepiped-shapedconfiguration (the thickness in the direction perpendicular to thedisplacement direction is large). The pair of thin plate sections 12 a,12 b are provided so that the side surface of the movable section 20 a,20 b is continuous to the side surface of the fixation section 14.Therefore, it is possible to selectively increase the rigidity ofpiezoelectric/electrostrictive device 10 in the Y axis direction.

[0145] That is, in the piezoelectric/electrostrictive device 10, it ispossible to selectively generate only the operation of the movablesection 20 a, 20 b in the plane (XZ plane). It is possible to suppressthe operation of the movable section 20 a, 20 b in the YZ plane(operation in the so-called flapping direction).

[0146] Next, explanation will be made for the respective constitutivecomponents of the piezoelectric/electrostrictive device 10 according tothis embodiment.

[0147] As described above, the movable section 20 a, 20 b is the portionwhich is operated on the basis of the driving amount of the thin platesection 12 a, 12 b, and a variety of members are attached theretodepending on the purpose of use of the piezoelectric/electrostrictivedevice 10. For example, when the piezoelectric/electrostrictive device10 is used as a displacement element, a shield plate for an opticalshutter or the like is attached thereto. Especially, when thepiezoelectric/electrostrictive device 10 is used for the mechanism forpositioning a magnetic head of a hard disk drive or for suppressing theringing, a member required to be positioned is attached thereto,including, for example, the magnetic head, a slider provided with themagnetic head, and a suspension provided with the slider.

[0148] As described above, the fixation section 14 is the portion forsupporting the thin plate sections 12 a, 12 b and the movable section 20a, 20 b. For example, when the fixation section 14 is utilized toposition the magnetic head of the hard disk drive, the entirepiezoelectric/electrostrictive device 10 is fixed by supporting andsecuring the fixation section 14, for example, to a carriage armattached to VCM (voice coil motor) or a fixation plate or a suspensionattached to the carriage arm. As shown in FIG. 1, the terminals 28, 30for driving the piezoelectric/electrostrictive elements 18 a, 18 b andother members are arranged on the fixation section 14 in some cases.

[0149] The material for constructing the movable section 20 a, 20 b andthe fixation section 14 is not specifically limited provided that it hasrigidity. However, it is possible to preferably use ceramics to whichthe ceramic green sheet-laminating method is applicable as describedlater on. Specifically, the material includes, for example, materialscontaining a major component of zirconia represented by fully stabilizedzirconia and partially stabilized zirconia, alumina, magnesia, siliconnitride, aluminum nitride, and titanium oxide, as well as materialscontaining a major component of a mixture of them. However, in view ofthe high mechanical strength and the high toughness, it is preferable touse a material containing a major component of zirconia, especiallyfully stabilized zirconia and a material containing a major component ofpartially stabilized zirconia. The metal material is not limitedprovided that it has rigidity. However, the metal material includes, forexample, stainless steel and nickel.

[0150] As described above, the thin plate section 12 a, 12 b is theportion which is driven in accordance with the displacement of thepiezoelectric/electrostrictive element 18 a, 18 b. The thin platesection 12 a, 12 b is the thin plate-shaped member having flexibility,and it functions to amplify the expansion and contracting displacementof the piezoelectric/electrostrictive element 18 a, 18 b arranged on thesurface as the bending displacement and transmit the displacement to themovable section 20 a, 20 b. Therefore, it is enough that the shape orthe material of the thin plate section 12 a, 12 b provides theflexibility with the mechanical strength of such a degree that it is notbroken by the bending displacement. It is possible to make appropriateselection considering the response performance and the operability ofthe movable section 20 a, 20 b.

[0151] It is preferable that the thickness Dd of the thin plate section12 a, 12 b is preferably about 2 μm to 100 μm. It is preferable that thecombined thickness of the thin plate section 12 a, 12 b and thepiezoelectric/electrostrictive element 18 a, 18 b is 7 μm to 500 μm. Itis preferable that the thickness of the electrode 24, 26 is 0.1 μm to 50μm, and the thickness of the piezoelectric/electrostrictive layer 22 is3 μm to 300 μm.

[0152] Ceramics, which is similarly used for the movable section 20 a,20 b and the fixation section 14, can be preferably used as the materialfor constructing the thin plate section 12 a, 12 b. A materialcontaining a major component of zirconia, especially fully stabilizedzirconia and a material containing a major component of partiallystabilized zirconia are most preferably used, because the mechanicalstrength is large even in the case of a thin wall thickness, thetoughness is high, and the reactivity with thepiezoelectric/electrostrictive layer and the electrode material issmall.

[0153] When the thin plate section 12 a, 12 b is made of a metalmaterial, it is enough that the metal material has flexibility and themetal material is capable of bending displacement as described above.However, preferably, it is desirable that the thin plate section 12 a,12 b is made of an iron-based material such as various stainless steelmaterials and various spring steel materials. Alternatively, it isdesirable that the thin plate section 12 a, 12 b is made of anon-ferrous material such as beryllium copper, phosphor bronze, nickel,and nickel-iron alloy.

[0154] Those which are fully stabilized or partially stabilized asfollows are preferably used as fully stabilized zirconia or partiallystabilized zirconia as described above. That is, the compound to be usedfor fully stabilizing or partially stabilizing zirconia includes yttriumoxide, ytterbium oxide, cerium oxide, calcium oxide, and magnesiumoxide. When at least one compound of them is added and contained, theobjective zirconia can be stabilized. Alternatively, the objectivezirconia can be stabilized as well, not only by adding one type of thecompound but also by adding a combination of the compounds.

[0155] The amount of addition of each of the compounds is desirably asfollows. That is, yttrium oxide or ytterbium oxide is added by 1 to 30mole %, preferably 1.5 to 10 mole %. Cerium oxide is added by 6 to 50mole %, preferably 8 to 20 mole %. Calcium oxide or magnesium oxide isadded by 5 to 40 mole %, preferably 5 to 20 mole %. Especially, it ispreferable to use yttrium oxide as a stabilizer. In this case, yttriumoxide is desirably added by 1.5 to 10 mole %, more preferably 2 to 4mole %. For example, alumina, silica, or transition metal oxide may beadded as an additive of sintering aid or the like in a range of 0.05 to20% by weight. However, when the sintering integration based on the filmformation method is adopted as a technique for forming thepiezoelectric/electrostrictive element 18 a, 18 b, it is also preferableto add, for example, alumina, magnesia, and transition metal oxide as anadditive.

[0156] In order to obtain the mechanical strength and the stable crystalphase, it is desirable that the average crystal grain size of zirconiais 0.05 to 3 μm, preferably 0.05 to 1 μm. As described above, ceramicscan be used for the thin plate section 12 a, 12 b in the same manner asin the movable section 20 a, 20 b and the fixation section 14.Preferably, it is advantageous to construct the thin plate sections 12a, 12 b with a substantially identical material in view of thereliability of the joined portion and the strength of thepiezoelectric/electrostrictive device 10, in order to reduce anycomplicated procedure of the production.

[0157] The piezoelectric/electrostrictive element 18 a, 18 b has atleast the piezoelectric/electrostrictive layer 22 and the pair ofelectrodes 24, 26 for applying the electric field to thepiezoelectric/electrostrictive layer 22. It is possible to use, forexample, piezoelectric/electrostrictive elements of the unimorph typeand the bimorph type. However, those of the unimorph type combined withthe thin plate section 12 a, 12 b are suitable for thepiezoelectric/electrostrictive device 10 as described above, becausethey are excellent in stability of the generated displacement amount andthey are advantageous to realize the light weight.

[0158] As shown in FIG. 1, the piezoelectric/electrostrictive element 18a, 18 b is preferably formed on the side surface side of the thin platesection 12 a, 12 b in view of the fact that the thin plate section 12 a,12 b can be driven to a greater extent.

[0159] Piezoelectric ceramics is preferably used for thepiezoelectric/electrostrictive layer 22. However, it is also possible touse electrostrictive ceramics, ferroelectric ceramics, oranti-ferroelectric ceramics. However, when thepiezoelectric/electrostrictive device 10 is used, for example, toposition the magnetic head of the hard disk drive, it is important toprovide the linearity concerning the displacement amount of the movablesection 20 a, 20 b and the driving voltage or the output voltage.Therefore, it is preferable to use a material having small strainhysteresis. It is preferable to use a material having a coerciveelectric field of not more than 10 kV/mm.

[0160] Specified materials include ceramics containing, for example,lead zirconate, lead titanate, lead magnesium niobate, lead nickelniobate, lead zinc niobate, lead manganese niobate, lead antimonystannate, lead manganese tungstate, lead cobalt niobate, bariumtitanate, sodium bismuth titanate, potassium sodium niobate, andstrontium bismuth tantalate singly or in mixture.

[0161] Especially, a material containing a major component of leadzirconate, lead titanate, and lead magnesium niobate, or a materialcontaining a major component of sodium bismuth titanate is preferablyused, in order to obtain the product having a stable composition with ahigh electromechanical coupling factor and a piezoelectric constant andwith small reactivity with the thin plate sections 12 a, 12 b (ceramics)during the sintering of the piezoelectric/electrostrictive layer 22.

[0162] It is also preferable to use ceramics obtained by adding, to thematerial described above, for example, oxides of lanthanum, calcium,strontium, molybdenum, tungsten, barium, niobium, zinc, nickel,manganese, cerium, cadmium, chromium, cobalt, antimony, iron, yttrium,tantalum, lithium, bismuth, and stannum singly or in mixture.

[0163] For example, when lanthanum and/or strontium is contained in themajor components of lead zirconate, lead titanate, and lead magnesiumniobate, an advantage is obtained in some cases, for example, in such away that the coercive electric field and the piezoelectriccharacteristic can be adjusted.

[0164] It is desirable to avoid the addition of a material such assilica which tends to form glass, because of the following reason. Thatis, the material such as silica tends to react with thepiezoelectric/electrostrictive material during the heat treatment forthe piezoelectric/electrostrictive layer 22. As a result, thecomposition is varied, and the piezoelectric characteristic isdeteriorated.

[0165] On the other hand, it is preferable that the pair of electrodes24, 26 of the piezoelectric/electrostrictive element 18 a, 18 b are madeof metal which is solid at room temperature and which is excellent inelectrical conductivity. For example, it is possible to use elementalsubstance or alloy of, for example, aluminum, titanium, chromium, iron,cobalt, nickel, copper, zinc, niobium, molybdenum, ruthenium, palladium,rhodium, silver, stannum, tantalum, tungsten, iridium, platinum, gold,and lead. It is also preferable to use a cermet material obtained bydispersing, in the metal described above, the same material as that ofthe piezoelectric/electrostrictive layer 22 or the thin plate section 12a, 12 b.

[0166] The material for the electrodes 24, 26 of thepiezoelectric/electrostrictive element 18 a, 18 b is selected anddetermined depending on the method for forming thepiezoelectric/electrostrictive layer 22. For example, when thepiezoelectric/electrostrictive layer 22 is formed by sintering on thefirst electrode 24 after the first electrode 24 is formed on the thinplate section 12 a, 12 b, it is necessary for the first electrode 24 touse high melting point metal such as platinum, palladium,platinum-palladium alloy, and silver-palladium alloy which does notchange at the sintering temperature for thepiezoelectric/electrostrictive layer 22. However, the electrodeformation can be performed at a low temperature for the second electrode26 which is formed on the piezoelectric/electrostrictive layer 22 afterforming the piezoelectric/electrostrictive layer 22. Therefore, it ispossible for the second electrode 26 to use low melting point metal suchas aluminum, gold, and silver.

[0167] The thickness of the electrode 24, 26 also serves as a factor toconsiderably decrease the displacement of thepiezoelectric/electrostrictive element 18 a, 18 b. Therefore, it ispreferable, especially for the electrode formed after the sintering ofthe piezoelectric/electrostrictive layer 22, to use organic metal pastecapable of obtaining a dense and thinner film after the sintering, forexample, a material such as gold resinate paste, platinum resinatepaste, and silver resinate paste.

[0168] The embodiment described above is illustrative of the case inwhich the thickness of the movable section 20 a, 20 b formed integrallyat the forward end portion of the thin plate section 12 a, 12 b isthicker than the thickness Dd of the thin plate section 12 a, 12 b.Alternatively, as in a piezoelectric/electrostrictive device 10 daccording to a fourth modified embodiment shown in FIG. 12, it is alsopreferable that the thickness of the movable section 20 a, 20 b isapproximately the same as the thickness Dd of the thin plate section 12a, 12 b. Accordingly, when a part or an article is attached to themovable section 20 a, 20 b, the part having a size corresponding to thedistance between the thin plate sections 12 a, 12 b can be attachedbetween the movable section 20 a, 20 b so that the part is interposedthereby. In this case, an adhesive area for attaching the part (forexample, the adhesive 38 shown in FIG. 7) corresponds to the movablesection 20 a, 20 b.

[0169] The piezoelectric/electrostrictive device 10 can be preferablyutilized for various sensors including, for example, ultrasonic sensors,acceleration sensors, angular velocity sensors, and mass sensors. Afurther advantage is obtained such that the sensitivity of the sensorcan be adjusted with ease by appropriately adjusting the size of theobject to be attached between the end surfaces 34 a, 34 b or between thethin plate sections 12 a, 12 b.

[0170] Next, piezoelectric/electrostrictive devices 10 e to 10 gaccording to fifth to seventh embodiments will be explained as morepreferred embodiments of the present invention with reference to FIGS.13 to 15.

[0171] At first, as shown in FIG. 13, the piezoelectric/electrostrictivedevice 10 e according to the fifth modified embodiment is constructed inapproximately the same manner as the piezoelectric/electrostrictivedevice explained above. However, for example, the arrangement of thepiezoelectric/electrostrictive element 18 a, 18 b differs in thefollowing points.

[0172] That is, the piezoelectric/electrostrictive element 18 a, 18 bcomprises the piezoelectric/electrostrictive layer 22 which has afour-layered structure. The first electrode 24 is formed to have acomb-shaped configuration to be located at the upper surface of thefirst layer and the upper surface of the third layer. The secondelectrode 26 is formed to have a comb-shaped configuration to be locatedat the lower surface of the first layer, the upper surface of the secondlayer, and the upper surface of the fourth layer.

[0173] Especially, the second electrode 26, which is located at thelower surface of the first layer, is formed substantially continuouslyranging over the respective side surfaces of the thin plate section 12a, 12 b, the movable section 20 a, 20 b, and the fixation section 14.Further, a part of the second electrode 26 is separated at the sidesurface of the fixation section 14 to form a slit 70.

[0174] The slit 70 is provided taking the following facts intoconsideration. That is, (1) the actuator is not driven at the rearwardend portion 72 of the piezoelectric/electrostrictive element 18 a, 18 b(portion ranging from the end of the slit 70 at the rearward end side tothe rearward end of the fixation section 14), (2) any short circuit isscarcely formed at the end of the first terminal 28, and (3) theelectrode material is arranged on the lower surface of thepiezoelectric/electrostrictive layer 22 at the rearward end portion ofthe piezoelectric/electrostrictive element 18 a, 18 b.

[0175] If the provision of the slit 70 is inversely unfavorable, it isnot necessarily indispensable to provide the slit 70. The slit 70 may beomitted.

[0176] In this embodiment, FIG. 13 is illustrative of the followingcase. That is, the thickness Dd of the thin plate section 12 a, 12 b is0.05 mm. The distance Dh from the side surface of the first thin platesection 12 a to the second thin plate section 12 b is 1.3 mm. The lengthDi of the fixation section 14 (length of the fixation section 14 in theaxial direction of the piezoelectric/electrostrictive device 10 f) is0.4 mm. The length Df of the movable section 20 a, 20 b is 0.3 mm. Thewidth Dj of the movable section 20 a, 20 b is 0.25 mm. The protrudingamount Dk of the movable section 20 a, 20 b is 0.05 mm. The entirelength Dm of the piezoelectric/electrostrictive device 10 f (distancefrom the forward end of the movable section 20 a, 20 b to the rearwardend of the fixation section 14) is 1.9 mm. The minimum distance betweenthe end surfaces 34 a, 34 b (corresponding to the distance Lc shown inFIG. 1) is 1.04 mm.

[0177] The dimension of each of the components is regulated within arange of ±10% with respect to each of the dimensions described above. Inthis embodiment, when the movable sections 20 a, 20 b are connected toone another with a spacer member 37 composed of the same material asthat of the constitutive member as shown in FIG. 7 between the endsurfaces 34 a, 34 b, it is possible to obtain thepiezoelectric/electrostrictive device having a resonance frequency of45±10 kHz and a displacement of not less than 0.5 μm (30 Vpp).

[0178]FIG. 13 is illustrative of the case in which the respective endsurfaces of the piezoelectric/electrostrictive layer 22 having thefour-layered structure are aligned. However, it is preferable that theend surfaces of the piezoelectric/electrostrictive layer 22 are disposedso that upper layers are gradually directed inwardly to provide steps.

[0179] Next, as shown in FIG. 14, the piezoelectric/electrostrictivedevice 10 f according to the sixth modified embodiment is constructed inapproximately the same manner as the piezoelectric/electrostrictivedevice 10 e according to the fifth modified embodiment. However, thearrangement of the piezoelectric/electrostrictive element 18 a, 18 bdiffers in the following points.

[0180] That is, the piezoelectric/electrostrictive element 18 a, 18 bcomprises the piezoelectric/electrostrictive layer 22 which has athree-layered structure. The first electrode 24 is formed to have acomb-shaped configuration to be located at a part of the lower surfaceof the first layer and the upper surface of the second layer. The secondelectrode 26 is formed to have a comb-shaped configuration to be locatedat a part of the lower surface of the first layer, the upper surface ofthe first layer, and the upper surface of the third layer.

[0181] Especially, the first electrode 24 and the second electrode 26,which are located at the lower surface of the first layer, are separatedfrom each other at a part of the thin plate section 12 a, 12 b by theaid of a slit 70. The second electrode, which is located at the lowersurface of the first layer, is formed continuously over a range from theslit 70 to the upper end of the movable section 20 a, 20 b. The firstelectrode 24, which is located at the lower surface of the first layer,is formed continuously over a range from the slit 70 to the rearward endof the fixation section 14.

[0182] Next, as shown in FIG. 15, the piezoelectric/electrostrictivedevice 10 g according to the seventh modified embodiment is constructedin approximately the same manner as the piezoelectric/electrostrictivedevice 10 f according to the sixth modified embodiment. However, theformation pattern of the pair of electrodes 24, 26 differs in thefollowing points.

[0183] That is, the first electrode 24 is formed to have a comb-shapedconfiguration to be located at the lower surface of the first layer andthe upper surface of the second layer of thepiezoelectric/electrostrictive layer 22. The second electrode 26 isformed to have a comb-shaped configuration to be located at the uppersurface of the first layer and the upper surface of the third layer ofthe piezoelectric/electrostrictive layer 22.

[0184] Especially, the first electrode 24, which is located at the lowersurface of the first layer, is formed continuously over the respectiveside surfaces of the thin plate section 12 a, 12 b, the movable section20 a, 20 b, and the fixation section 14.

[0185] The difference from the piezoelectric/electrostrictive device 10f according to the sixth modified embodiment will now be explained. Asshown in FIG. 14, in the piezoelectric/electrostrictive device 10 faccording to the sixth modified embodiment, both of the first electrode24 and the second electrode 26 are formed on the thin plate section 12a. Therefore, the electrodes 24, 26, which have the mutually oppositepolarities, are located at the both ends of thepiezoelectric/electrostrictive element 18, 18 b (the end correspondingto the forward end of the movable section 20 a, 20 b and the endcorresponding to the rearward end of the fixation section 14).

[0186] On the other hand, as shown in FIG. 15, in thepiezoelectric/electrostrictive device log according to the seventhmodified embodiment, only the first electrode 24 is formed on the thinplate section 12 a, 12 b. Therefore, the electrodes 24, which have themutually identical polarity, are located at the both ends of thepiezoelectric/electrostrictive element 18 a, 18 b. The feature of thepolarity at the end as described above is utilized by appropriatelymaking combination with a circuit for which thepiezoelectric/electrostrictive device 10 g is utilized.

[0187] The substantial driving portion of thepiezoelectric/electrostrictive element 18 a, 18 b is the portion atwhich the pair of electrodes 24, 26 are overlapped with each other. Inthe piezoelectric/electrostrictive device 10 f according to the sixthmodified embodiment, as shown in FIG. 14, the substantial drivingportion is the portion at which the electrodes 24, 26 formed at therespective layers of the piezoelectric/electrostrictive layer 22 areoverlapped with each other, which resides in one part corresponding tothe portion indicated by the range C.

[0188] On the other hand, the substantial driving portion of thepiezoelectric/electrostrictive device 10 f according to the seventhmodified embodiment resides in two parts, i.e., the portion (portionindicated by the range C) at which the electrodes 24, 26 formed at therespective layers of the piezoelectric/electrostrictive layer 22 areoverlapped with each other, and the portion (portion indicated by therange D) which is disposed at the position deviated toward the movablesection 20 a, 20 b with respect to the end of the first electrode 24formed at the upper surface of the second layer of thepiezoelectric/electrostrictive layer 22 and at which the pair ofelectrodes 24, 26 are overlapped with each other with the first layer ofthe piezoelectric/electrostrictive layer 22 intervening therebetween.The piezoelectric/electrostrictive device log according to the seventhmodified embodiment is characterized in that the portion indicated bythe range D also serves as the driving source.

[0189] Next, explanation will be made with reference to FIGS. 16 to 40for several methods for producing the piezoelectric/electrostrictivedevice 10 according to the embodiment of the present invention.

[0190] Ceramics is preferably used for the constitutive material foreach of the members of the piezoelectric/electrostrictive device 10according to the embodiment of the present invention. It is preferablethat the constitutive elements of the piezoelectric/electrostrictivedevice 10 concerning the substrate 16 except for thepiezoelectric/electrostrictive elements 18 a, 18 b, i.e., the thin platesections 12 a, 12 b, the fixation section 14, and the movable sections20 a, 20 b are produced by using the ceramic green sheet-laminatingmethod. On the other hand, it is preferable that thepiezoelectric/electrostrictive elements 18 a, 18 b as well as therespective terminals 28, 30 are produced by using the film formationmethod, for example, for the thin film and the thick film.

[0191] According to the ceramic green sheet-laminating method in whichthe respective members of the substrate 16 of thepiezoelectric/electrostrictive device 10 can be formed in an integratedmanner, the time-dependent change of state scarcely occurs at the joinedportions of the respective members. Therefore, this method provides thehigh reliability of the joined portion, and it is advantageous to ensurethe rigidity.

[0192] In the piezoelectric/electrostrictive device 10 according to thisembodiment, the boundary portion (joined portion) between the thin platesection 12 a, 12 b and the fixation section 14 and the boundary portion(joined portion) between the thin plate section 12 a, 12 b and themovable section 20 a, 20 b function as supporting points for expressingthe displacement. Therefore, the reliability of the joined portion is animportant point which dominates the characteristic of thepiezoelectric/electrostrictive device 10.

[0193] The production methods described below are excellent inreproducibility and formability. Therefore, it is possible to obtain thepiezoelectric/electrostrictive device 10 having a predetermined shapewithin a short period of time with good reproducibility.

[0194] A first production method for the piezoelectric/electrostrictivedevice 10 according to the embodiment of the present invention will bespecifically explained below. The following definitions are now made.The laminate, which is obtained by laminating the ceramic green sheets,is defined to be the ceramic green laminate 58 (see, for example, FIG.17). The integrated matter, which is obtained by sintering the ceramicgreen laminate 58, is defined to be the ceramic laminate 60 (see, forexample, FIG. 18). The integrated matter comprising the movable sections20 a, 20 b, the thin plate sections 12 a, 12 b, and the fixation section14, which is obtained by cutting off unnecessary portions from theceramic laminate 60, is defined to be the ceramic substrate 16C (seeFIG. 19).

[0195] In the first production method, the ceramic laminate 60 isfinally cut into chip units in a form in which a plurality ofpiezoelectric/electrostrictive devices 10 are arranged in the verticaldirection and in the lateral direction respectively on an identicalsubstrate to produce a large number of piezoelectric/electrostrictivedevices 10 in accordance with identical steps. However, in order tosimplify the explanation, description will be made principally for thecase in which one individual of piezoelectric/electrostrictive device 10is produced.

[0196] At first, for example, a binder, a solvent, a dispersing agent,and a plasticizer are added and mixed with a ceramic powder such aszirconia to prepare a slurry. The slurry is subjected to a degassingtreatment, and then a ceramic green sheet having a predeterminedthickness is prepared in accordance with, for example, the reverse rollcoater method and the doctor blade method.

[0197] Subsequently, the ceramic green sheet is processed into thosehaving various shapes as shown in FIG. 16 in accordance with, forexample, a method such as the punching out based on the mold and thelaser machining to obtain a plurality of ceramic green sheets 50A to50I, 52A, 52B for forming the substrate.

[0198] The ceramic green sheets 50A to 50I, 52A, 52B include theplurality (for example, nine) of ceramic green sheets 50A to 50I each ofwhich is formed with at least a window 54 for forming the space betweenthe thin plate sections 12 a, 12 b, and the plurality (for example, two)of ceramic green sheets 52A, 52B to be formed into the thin platesections 12 a, 12 b thereafter. The numbers of ceramic green sheetsreferred to above are persistently by way of example.

[0199] After that, as shown in FIG. 17, the ceramic green sheets 50A to50I, 52A, 52B are laminated and secured under pressure so that theceramic green sheets 50A to 50I are interposed between the ceramic greensheets 52A, 52B to form a ceramic green laminate 58. Subsequently, theceramic green laminate 58 is sintered to obtain a ceramic laminate 60(see FIG. 18).

[0200] It is noted that there is no limitation for the number ofpressure-securing process or processes and the sequence for the purposeof the lamination and integration into one unit. These factors can beappropriately determined depending on the structure, for example, sothat the desired structure is obtained on the basis of, for example, theshape of the window 54 and the number of ceramic green sheets.

[0201] It is unnecessary that the shape of the window 54 is identical inall cases. The shape of the window 54 can be determined depending on thedesired function. There is also no limitation for the number of ceramicgreen sheets and the thickness of each of the ceramic green sheets.

[0202] In the pressure-securing process, it is possible to furtherimprove the laminating performance by applying the heat. The laminatingperformance at the boundary of the ceramic green sheet can be improvedby providing an auxiliary joining layer, for example, by applying andprinting, onto the ceramic green sheet, a paste or a slurry principallycontaining a ceramic powder (it is preferable to use a composition whichis the same as or similar to that of the ceramics used for the ceramicgreen sheet in order to ensure the reliability), and a binder. When theceramic green sheets 52A, 52B are thin, it is preferable to handle themwith a plastic film, especially with a polyethylene terephthalate filmcoated with a releasing agent based on silicone on the surface.

[0203] Subsequently, as shown in FIG. 18, thepiezoelectric/electrostrictive elements 18 a, 18 b are formedrespectively on the both surfaces of the ceramic laminate 60, i.e., onthe surfaces corresponding to the surfaces at which the ceramic greensheets 52A, 52B are laminated. Those usable as the method for formingthe piezoelectric/electrostrictive elements 18 a, 18 b include the thickfilm formation method such as the screen printing method, the dippingmethod, the coating method, and the electrophoresis method, and the thinfilm formation method such as the ion beam method, the sputteringmethod, the vacuum vapor deposition, the ion plating method, thechemical vapor deposition method (CVD), and the plating.

[0204] When the piezoelectric/electrostrictive elements 18 a, 18 b areformed by using the film formation method as described above, thepiezoelectric/electrostrictive elements 18 a, 18 b and the thin platesections 12 a, 12 b can be integrally joined and arranged without usingany adhesive. It is possible to ensure the reliability and thereproducibility, and it is easy to form the stack.

[0205] In this case, it is preferable that thepiezoelectric/electrostrictive elements 18 a, 18 b are formed by meansof the thick film formation method, because of the following reason.That is, especially, when the piezoelectric/electrostrictive layer 22 isformed by using the thick film formation method, the film can be formedby using, for example, a paste, a slurry, a suspension, an emulsion, ora sol containing a major component of particles or powder ofpiezoelectric ceramics having an average particle size of 0.01 to 5 μm,preferably 0.05 to 3 μm. It is possible to obtain goodpiezoelectric/electrostrictive characteristics by sintering the formedfilm.

[0206] The electrophoresis method is advantageous in that the film canbe formed at a high density with a high shape accuracy. The screenprinting method is advantageous to simplify the production step, becauseit is possible to simultaneously perform the film formation and thepattern formation.

[0207] Explanation will be specifically made for the formation of thepiezoelectric/electrostrictive elements 18 a, 18 b. At first, theceramic green laminate 58 is sintered and integrated into one unit at atemperature of 1200° C. to 1600° C. to obtain the ceramic laminate 60.After that, the first ones of the first electrodes 24 for the thin platesections 12 a, 12 b are printed and sintered at predetermined positionson the both surfaces of the ceramic laminate 60. Subsequently, thepiezoelectric/electrostrictive layers 22 are printed and sintered.Further, the second electrodes 26, which form the pairs with the firstones of the first electrodes 24, are printed and sintered to form thepiezoelectric/electrostrictive elements 18 a, 18 b by repeating theforegoing steps in a predetermined number of times (when thepiezoelectric/electrostrictive element 18 a, 18 b is composed of themultilayered piezoelectric/electrostrictive layer 22). After that, theterminals 28, 30 are printed and sintered in order to electricallyconnect the respective electrodes 24, 26 to the driving circuit.

[0208] Alternatively, the following process may be available. That is,the first one of the first electrode 24 at the lowermost layer isprinted and sintered. The piezoelectric/electrostrictive layer 22 andthe first one of the second electrode 26 which forms the pair with thefirst one of the first electrode 24 are printed and sintered. Theprinting and the sintering are repeated in a predetermined number oftimes with the foregoing process unit to form thepiezoelectric/electrostrictive element 18 a, 18 b.

[0209] In this process, when the materials are selected so that thesintering temperature for each of the members is lowered in accordancewith the stacking sequence, for example, when platinum (Pt) is used forthe first electrode 24, lead zirconate titanate (PZT) is used for thepiezoelectric/electrostrictive layer 22, gold (Au) is used for thesecond electrode 26, and silver (Ag) is used for the terminals 28, 30,then the material, which has been already sintered beforehand, is notsintered again at a certain sintering stage. Thus, it is possible toavoid the occurrence of inconvenience such as peeling off andaggregation of the electrode material or the like.

[0210] When appropriate materials are selected, it is also possible tosuccessively print the respective members of thepiezoelectric/electrostrictive elements 18 a, 18 b and the terminals 28,30, followed by the sintering one time. Further, it is also possible toprovide, for example, the electrode 26 at the outermost layer at a lowtemperature after forming the piezoelectric/electrostrictive layer 22 atthe outermost layer.

[0211] Alternatively, the respective members of thepiezoelectric/electrostrictive elements 18 a, 18 b and the terminals 28,30 may be formed by means of the thin film formation method such as thesputtering method and the vapor deposition method. In this case, it isnot necessarily indispensable to perform the heat treatment.

[0212] When the piezoelectric/electrostrictive elements 18 a, 18 b areformed, it is also preferable that the piezoelectric/electrostrictiveelements 18 a, 18 b are previously formed on the both surfaces of theceramic green laminate 58, i.e., on the respective surfaces of theceramic green sheets 52A, 52B, and the ceramic green laminate 58 and thepiezoelectric/electrostrictive elements 18 a, 18 b are simultaneouslysintered or co-fired. For example, the following methods are availableto perform the co-firing.

[0213] That is, the sintering may be performed for all of theconstitutive films of the ceramic green laminate 58 and thepiezoelectric/electrostrictive elements 18 a, 18 b. The first electrodes24 and the ceramic green laminate 58 may be co-fired, or the otherconstitutive films except for the second electrodes 26 and the ceramicgreen laminate 58 may be co-fired.

[0214] The following method is available to co-fire thepiezoelectric/electrostrictive elements 18 a, 18 b and the ceramic greenlaminate 58. That is, precursors of the piezoelectric/electrostrictivelayers 22 are formed, for example, in accordance with the tape formationmethod based on the use of a slurry material. The precursors of thepiezoelectric/electrostrictive layers 22 before the sintering arelaminated on the surfaces of the ceramic green laminate 58, for example,by means of the thermal securing process under pressure, followed by theco-firing to simultaneously produce the movable sections 20 a, 20 b, thethin plate sections 12 a, 12 b, the piezoelectric/electrostrictivelayers 22, and the fixation section 14. However, in this method, it isnecessary to form the electrodes 24 beforehand on the surfaces of theceramic green laminate 58 and/or on the piezoelectric/electrostrictivelayers 22 by using the film formation method described above.

[0215] Another method is also available. That is, the electrodes 24, 26and the piezoelectric/electrostrictive layers 22, which are therespective constitutive layers of the piezoelectric/electrostrictiveelements 18 a, 18 b, are formed by means of the screen printing onportions to be finally formed into at least the thin plate sections 12a, 12 b of the ceramic green laminate 58, followed by the co-firing.

[0216] The sintering temperature for the constitutive film of thepiezoelectric/electrostrictive element 18 a, 18 b is appropriatelydetermined depending on the material for constructing the same. However,the sintering temperature is generally 500° C. to 1500° C. The sinteringtemperature is preferably 1000° C. to 1400° C. for thepiezoelectric/electrostrictive layer 22. In this case, in order tocontrol the composition of the piezoelectric/electrostrictive layer 22,the sintering is preferably performed in the presence of an evaporationsource of the material of the piezoelectric/electrostrictive layer 22.When the piezoelectric/electrostrictive layers 22 and the ceramic greenlaminate 58 are co-fired, it is necessary to conform the sinteringconditions of the both.

[0217] The piezoelectric/electrostrictive element 18 a, 18 b is notnecessarily formed on the both surfaces of the ceramic laminate 60 orthe ceramic green laminate 58. It is of course allowable to form thepiezoelectric/electrostrictive element 18 a, 18 b on only one surface.

[0218] Subsequently, unnecessary portions are cut off from the ceramiclaminate 60 formed with the piezoelectric/electrostrictive elements 18a, 18 b as described above. The cutoff positions are located at sideportions of the ceramic laminate 60, especially at portions at which thehole 42 based on the window 54 is formed on the side surfaces of theceramic laminate 60 by means of the cutoff (see cutting lines C1 andC2).

[0219] Subsequently, as shown in FIG. 19, a central portion 20 c of theportion to be formed into the movable sections 20 a, 20 b is cut andremoved along cutting lines C3 and C4 to produce thepiezoelectric/electrostrictive device 10 comprising thepiezoelectric/electrostrictive elements 18 a, 18 b formed on the ceramicsubstrate 16C integrated with the movable sections 20 a, 20 b, the thinplate sections 12 a, 12 b, and the fixation section 14. Those applicableas the cutoff method include the mechanical machining such as the dicingmachining and the wire saw machining as well as the electron beammachining and the laser machining based on the use of, for example, theYAG laser and the excimer laser.

[0220] When the ceramic substrate 16C is cut off, the machining may beperformed by combining the machining methods described above. Forexample, the wire saw machining is preferably performed for the cuttinglines C1 and C2 (see FIG. 18). The dicing machining is preferablyperformed for the end surfaces 34 a, 34 b of the movable sections 20 a,20 b and the fixation section 14 perpendicular to the cutting lines C1and C2.

[0221] In the first production method for thepiezoelectric/electrostrictive device 10 described above, thepiezoelectric/electrostrictive elements 18 a, 18 b are formed on thethin plate sections 12 a, 12 b by means of the integrated sintering.Therefore, as shown in FIG. 20A, for example, the thin plate sections 12a, 12 b and the piezoelectric/electrostrictive elements 18 a, 18 b areslightly displaced to be convex toward the hole 42, giving a state inwhich the strain is generated in shape, for example, due to theshrinkage of the piezoelectric/electrostrictive layers 22 caused duringthe sintering and the difference in coefficient of thermal expansionamong the pair of electrodes 24, 26, the piezoelectric/electrostrictivelayers 22, and the thin plate sections 12 a, 12 b. As a result, theinternal residual stress tends to arise in thepiezoelectric/electrostrictive elements 18 a, 18 b (especially in thepiezoelectric/electrostrictive layers 22) and in the thin plate sections12 a, 12 b.

[0222] The internal residual stress in the thin plate sections 12 a, 12b and the piezoelectric/electrostrictive layers 22 is generated when theintegrated sintering is performed as described above as well as whenseparate members of the piezoelectric/electrostrictive elements 18 a, 18b are bonded to the thin plate sections 12 a, 12 b, for example, with anadhesive. That is, the internal residual stress is generated in the thinplate sections 12 a, 12 b and the piezoelectric/electrostrictive layers22 due to the curing and shrinkage of the adhesive or the like when theadhesive is immobilized or cured. When the heating is required for theimmobilization or the curing, the internal residual stress is increased.

[0223] If the piezoelectric/electrostrictive device 10 is used in thisstate, the movable sections 20 a, 20 b do not exhibit any desireddisplacement in some cases, even when the predetermined electric fieldis applied to the piezoelectric/electrostrictive layers 22, because ofthe following reason. That is, the material characteristic of thepiezoelectric/electrostrictive layers 22 and the displacement action ofthe movable sections 20 a, 20 b are inhibited by the internal residualstress generated in the thin plate sections 12 a, 12 b and thepiezoelectric/electrostrictive layers 22.

[0224] In the first production method, as shown in FIG. 20A, the centralportion 20 c of the movable section 20 a, 20 b is cut off by apredetermined width W1 (for example, 100 μm). When the central portion20 c is cut off, the mutually opposing end surfaces 34 a, 34 b areformed for the movable sections 20 a, 20 b as shown in FIG. 20B. The endsurfaces 34 a, 34 b are moved to make approach to one another by theinternal residual stress having been generated in the thin platesections 12 a, 12 b and the piezoelectric/electrostrictive layers 22.The width between the respective end surfaces 34 a, 34 b after themovement is, for example, a second predetermined width W2 (for example,30 μm) which is shorter than the predetermined width W1. Morespecifically, the second predetermined width W2 is shorter at forwardend portions.

[0225] The movement of the end surfaces 34 a, 34 b results from therelease of the internal residual stress having been generated in thethin plate sections 12 a, 12 b and the piezoelectric/electrostrictivelayers 22. When the piezoelectric/electrostrictive device 10 is used ina state in which the internal residual stress is released, then themovable sections 20 a, 20 b exhibit the displacement action asapproximately designed, and the good device characteristic is exhibited.This effect is equivalently obtained when a part of the portion to beformed into the fixation section 14 is cut off to form the mutuallyopposing end surfaces 34 a, 34 b for the fixation section 14, forexample, as shown in FIG. 11. In this case, the internal residualstress, which has been generated in the thin plate sections 12 a, 12 band the piezoelectric/electrostrictive layers 22, is released by themovement of the mutually opposing end surfaces 34 a, 34 b formed for thefixation section 14. The mutually opposing end surfaces 34 a, 34 b arenot necessarily formed by cutting off the central portion of the movablesection 20 a, 20 b or the fixation section 14. An equivalent effect isalso obtained even when the mutually opposing end surfaces 34 a, 34 bare formed by cutting a portion deviated from the center.

[0226] When the cutoff as shown in FIG. 18 and the cutoff as shown inFIG. 19 are performed, it is preferable that the heat treatment isperformed at 300° C. to 800° C. after the cutoff, because of thefollowing reason. That is, any defect such as microcrack tends to occurin the piezoelectric/electrostrictive device 10 as a result of themachining, while the defect can be removed by means of the heattreatment described above, and the reliability is improved. Further, itis preferable to apply the aging treatment by being left to stand for atleast about 10 hours at a temperature of about 80° C. after the heattreatment, because of the following reason. That is, when the agingtreatment is performed, for example, the various stresses, which havebeen exerted during the production process, can be further mitigated tocontribute to the improvement in characteristic.

[0227] Next, a second production method will be explained with referenceto FIGS. 21 to 24. At first, as shown in FIG. 21, a plurality (forexample, four) of ceramic green sheets 50A to 50D each of which isformed with a window 54 for forming at least the space between the thinplate sections 12 a, 12 b, a plurality (for example, seven) of ceramicgreen sheets 102A to 102G each of which is continuously formed with awindow 54 for forming the space between the thin plate sections 12 a, 12b and a window 100 for forming the movable sections 20 a, 20 b havingthe mutually opposing end surfaces 34 a, 34 b, and a plurality (forexample, two) of ceramic green sheets 52A, 52B to be formed into thethin plate sections 12 a, 12 b thereafter are prepared.

[0228] After that, as shown in FIG. 22, the ceramic green sheets 50A to50D, 52A, 52B, 102A to 102G are laminated and secured under pressure sothat the ceramic green sheets 50A to 50D, 102A to 102G are interposedbetween the ceramic green sheets 52A, 52B to form a ceramic greenlaminate 58. The lamination is performed while the ceramic green sheets102A to 102G are positioned at the center. During this process, theremay be portions on which no pressure is applied during the securingunder pressure, due to the presence of the window 100. Therefore, forexample, it is necessary that the order of the lamination and thepressure-securing is changed so that such portions do not appear. Thisprocedure is also significant in third and fourth production methodsdescribed later on. After that, the ceramic green laminate 58 issintered to obtain a ceramic laminate 60 (see FIG. 23).

[0229] Subsequently, as shown in FIG. 23, thepiezoelectric/electrostrictive elements 18 a, 18 b having themultilayered structure are formed respectively on the both surfaces ofthe ceramic laminate 60, i.e., on the surfaces corresponding to thesurfaces at which the ceramic green sheets 52A, 52B are laminatedrespectively. The piezoelectric/electrostrictive elements 18 a, 18 b areintegrated into the ceramic laminate 60 by means of the sintering. Ofcourse, it is allowable to form the piezoelectric/electrostrictiveelement 18 on only one side surface. This fact also holds for the thirdand fourth production methods described later on.

[0230] Subsequently, the ceramic laminate 60, which is formed with thepiezoelectric/electrostrictive elements 18 a, 18 b, is cut along cuttinglines C1, C2, C5 to thereby cut off side portions and forward endportions of the ceramic laminate 60. As a result of the cutoff, as shownin FIG. 24, the piezoelectric/electrostrictive device 10 is obtained,which is formed with the movable sections 20 a, 20 b having the mutuallyopposing end surfaces 34 a, 34 b in which thepiezoelectric/electrostrictive elements 18 a, 18 b are formed on theceramic substrate 16C. The following cutting timing is available. Thatis, the ceramic laminate 60 may be cut along the cutting lines C1 andC2, and then it may be cut along the cutting line C5. Alternatively, theceramic laminate 60 may be cut along the cutting line C5, and then itmay be cut along the cutting lines C1 and C2. Of course, it is alsopreferable to perform the foregoing cutting procedures at the same time.The end of the fixation section 14, which is opposed to the cutting lineC5, may be appropriately cut.

[0231] In the second production method, thepiezoelectric/electrostrictive elements 18 a, 18 b are formed on theceramic substrate 16C simultaneously with the cutoff of the unnecessaryportions from the ceramic laminate 60, making it possible to obtain thepiezoelectric/electrostrictive device 10 formed with the movablesections 20 a, 20 b having the mutually opposing end surfaces 34 a, 34b. Accordingly, it is possible to simplify the production steps.Further, it is possible to improve the yield of thepiezoelectric/electrostrictive device 10. In this procedure, it isespecially preferable that a plurality of piezoelectric/electrostrictivedevices 10 are arranged in the vertical direction and in the lateraldirection respectively on an identical substrate to produce a largenumber of piezoelectric/electrostrictive devices 10 in accordance withidentical steps, because of the following reason. That is, a largenumber of individuals are easily dealt with in the identical stepconcerning the formation of the end surfaces 34 a, 34 b as compared withthe first production method.

[0232] Next, a third production method will be explained with referenceto FIGS. 25 to 28. At first, as shown in FIG. 25, a plurality (forexample, four) of ceramic green sheets 50A to 50D each of which isformed with a window 54 for forming at least the space between the thinplate sections 12 a, 12 b, a plurality (for example, seven) of ceramicgreen sheets 108A to 108G each of which is continuously formed with awindow 54 for forming the space between the thin plate sections 12 a, 12b and a window 104 for forming a portion 20D (see FIG. 28) to be formedinto the movable sections 20 a, 20 b with the mutually opposing endsurfaces 34 a, 34 b partially connected to one another and which isformed with a projection 106 partially protruding toward the window 54,and a plurality (for example, two) of ceramic green sheets 52A, 52B tobe formed into the thin plate sections 12 a, 12 b thereafter areprepared.

[0233] After that, as shown in FIG. 26, the ceramic green sheets 50A to50D, 52A, 52B, 108A to 108G are laminated and secured under pressure sothat the ceramic green sheets 50A to 50D, 108A to 108G are interposedbetween the ceramic green sheets 52A, 52B to form a ceramic greenlaminate 58. The lamination is performed while the ceramic green sheets108A to 108G are positioned at the center. After that, the ceramic greenlaminate 58 is sintered to obtain a ceramic laminate 60 (see FIG. 27).

[0234] Subsequently, as shown in FIG. 27, thepiezoelectric/electrostrictive elements 18 a, 18 b having themultilayered structure are formed respectively on the both surfaces ofthe ceramic laminate 60, i.e., on the surfaces corresponding to thesurfaces at which the ceramic green sheets 52A, 52B are laminated. Thepiezoelectric/electrostrictive elements 18 a, 18 b are integrated intothe ceramic laminate 60 by means of the sintering.

[0235] Subsequently, the ceramic laminate 60, which is formed with thepiezoelectric/electrostrictive elements 18 a, 18 b, is cut along cuttinglines C1, C2, C5 to thereby cut off side portions and forward endportions of the ceramic laminate 60. As a result of the cutoff, as shownin FIG. 28, the fixation section 14, the thin plate sections 12 a, 12 b,and the piezoelectric/electrostrictive elements 18 a, 18 b are formed.However, the portion 20D to be formed into the movable sections 20 a, 20b is in a state in which the mutually opposing end surfaces 34 a, 34 bare partially connected to one another by the projection 106.

[0236] Subsequently, the projection 106, which partially connects themutually opposing end surfaces 34 a, 34 b, is cut off to produce thepiezoelectric/electrostrictive device 10 in which thepiezoelectric/electrostrictive elements 18 a, 18 b are formed on theceramic substrate 16C integrated with the movable sections 20 a, 20 b,the thin plate sections 12 a, 12 b, and the fixation section 14.

[0237] In the third production method, it is enough that the slenderprojection 106, which partially connects the mutually opposing endsurfaces 34 a, 34 b, is cut off at the final stage. Accordingly, thecutoff procedure can be performed easily and reliably, and thus it ispossible to simplify the production steps. Further, it is possible toimprove the yield of the piezoelectric/electrostrictive device 10.

[0238] Next, a fourth production method will be explained with referenceto FIGS. 29 to 32. At first, as shown in FIG. 29, a plurality (forexample, four) of ceramic green sheets 50A to 50D each of which isformed with a window 54 for forming at least the space between the thinplate sections 12 a, 12 b, a plurality (for example, seven) ceramicgreen sheets 114A to 114G each of which is formed with a window 54 forforming the space between the thin plate sections 12 a, 12 b and awindow 104 for forming a portion 20D (see FIG. 32) to be formed into themovable sections 20 a, 20 b with the mutually opposing end surfaces 34a, 34 b partially connected to one another and which is formed with acrosspiece 112 to separate the window 54 and the window 104 from eachother, and a plurality (for example, two) of ceramic green sheets 52A,52B to be formed into the thin plate sections 12 a, 12 b thereafter areprepared.

[0239] After that, as shown in FIG. 30, the ceramic green sheets 50A to50D, 52A, 52B, 114A to 114G are laminated and secured under pressure sothat the ceramic green sheets 50A to 50D, 114A to 114G are interposedbetween the ceramic green sheets 52A, 52B to form a ceramic greenlaminate 58. The lamination is performed while the ceramic green sheets114A to 114G are positioned at the center. After that, the ceramic greenlaminate 58 is sintered to obtain a ceramic laminate 60 (see FIG. 31).

[0240] Subsequently, as shown in FIG. 31, thepiezoelectric/electrostrictive elements 18 a, 18 b having themultilayered structure are formed respectively on the both surfaces ofthe ceramic laminate 60, i.e., on the surfaces corresponding to thesurfaces at which the ceramic green sheets 52A, 52B are laminated. Thepiezoelectric/electrostrictive elements 18 a, 18 b are integrated intothe ceramic laminate 60 by means of the sintering.

[0241] Subsequently, the ceramic laminate 60, which is formed with thepiezoelectric/electrostrictive elements 18 a, 18 b, is cut along cuttinglines C1, C2, C5 to thereby cut off side portions and forward endportions of the ceramic laminate 60. As a result of the cutoff, as shownin FIG. 32, the fixation section 14, the thin plate sections 12 a, 12 b,and the piezoelectric/electrostrictive elements 18 a, 18 b are formed.However, the portion 20D to be formed into the movable sections 20 a, 20b is in a state in which the mutually opposing end surfaces 34 a, 34 bare partially connected to one another by the crosspiece 112.

[0242] Subsequently, the crosspiece 112, which partially connects themutually opposing end surfaces 34 a, 34 b, is cut off to produce thepiezoelectric/electrostrictive device 10 in whichpiezoelectric/electrostrictive elements 18 a, 18 b are formed on theceramic substrate 16C integrated with the movable sections 20 a 20 b,thin plate sections 12 a, 12 b, and the fixation section 14.

[0243] In the fourth production method, it is enough that the crosspiece112, which partially connects the mutually opposing end surfaces 34 a,34 b, is cut off at the final stage. Accordingly, the cutoff procedurecan be performed easily and reliably, and thus it is possible tosimplify the production steps. Further, it is possible to improve theyield of the piezoelectric/electrostrictive device 10.

[0244] The embodiments described above are illustrative of the case inwhich the movable sections 20 a, 20 b, the fixation section 14, and thethin plate sections 12 a, 12 b are constructed by the ceramic substrate16C. Alternatively, each of the parts may be made of a metal material.Further alternatively, each of the parts may be made to provide a hybridstructure obtained by combining those produced with materials ofceramics and metal. In this case, in order to join the metal materialsto one another and/or join the ceramic and metal materials to oneanother, it is possible to use adhesion with organic resin or glass,brazing, soldering, eutectic bonding, or welding.

[0245] Explanation will be made with reference to FIGS. 33 to 40, forexample, for production methods (fifth and sixth production methods) fora piezoelectric/electrostrictive device (piezoelectric/electrostrictivedevice 10 h according to an eighth modified embodiment) having thehybrid structure in which the movable sections 20 a, 20 b and thefixation section 14 are made of ceramics, and the thin plate sections 12a, 12 b are made of metal. Therefore, the substrate containing metal andceramics, which is produced by the fifth and sixth production methods,is referred to as the substrate 16D.

[0246] In the fifth production method, at first, as shown in FIG. 33, aplurality (for example, four) of ceramic green sheets 50A to 50D each ofwhich is formed with a window 54 for forming at least the space betweenthe thin plate sections 12 a, 12 b, and a plurality (for example, seven)ceramic green sheets 102A to 102G each of which is continuously formedwith a window 54 for forming the space between the thin plate sections12 a, 12 b and a window 100 for forming the movable sections 20 a, 20 bhaving the mutually opposing end surfaces 34 a, 34 b are prepared.

[0247] After that, as shown in FIG. 34, the ceramic green sheets 50A to50D, 102A to 102G are laminated and secured under pressure to form aceramic green laminate 158. The lamination is performed while theceramic green sheets 102A to 102G are positioned at the center. Afterthat, as shown in FIG. 35, the ceramic green laminate 158 is sintered toobtain a ceramic laminate 160. At this stage, the ceramic laminate 160is formed such that the hole 130 is formed by the windows 54, 100.

[0248] Subsequently, as shown in FIG. 36, thepiezoelectric/electrostrictive elements 18 a, 18 b, which areconstructed as separate members, are respectively bonded with an epoxyadhesive to the surfaces of metal plates 152A, 152B to serve as the thinplate sections 12 a, 12 b. The separate members of thepiezoelectric/electrostrictive elements 18 a, 18 b can be formed, forexample, in accordance with the ceramic green sheet-laminating method.

[0249] Subsequently, the metal plates 152A, 152B are bonded to theceramic laminate 160 with the epoxy adhesive so that the ceramiclaminate 160 is interposed between the metal plates 152A, 152B and thehole 130 is closed thereby to provide a hybrid laminate 162 (see FIG.37).

[0250] Subsequently, as shown in FIG. 37, the hybrid laminate 162, whichis formed with the piezoelectric/electrostrictive elements 18 a, 18 b,is cut along cutting lines C1, C2, C5 to thereby cut off side portionsand forward end portions of the hybrid laminate 162. As a result of thecutoff, as shown in FIG. 38, the piezoelectric/electrostrictive device10 h according to the eighth modified embodiment is obtained, in whichthe piezoelectric/electrostrictive elements 18 a, 18 b are formed on thethin plate sections 12 a, 12 b constituted by the metal plates, of thesubstrate 16D, and the movable sections 20 a, 20 b having the mutuallyopposing end surfaces 34 a, 34 b are formed.

[0251] On the other hand, in the sixth production method, at first, asshown in FIG. 34, ceramic green sheets 50A to 50D, 102A to 102G arelaminated and secured under pressure to form a ceramic green laminate158. After that, the ceramic green laminate 158 is sintered to obtain aceramic laminate 160 as shown in FIG. 39. At this stage, the ceramiclaminate 160 is formed such that the hole 130 is formed by the windows54, 100.

[0252] Subsequently, as shown in FIG. 40, the metal plates 152A, 152Bare bonded to the ceramic laminate 160 with an epoxy adhesive so thatthe ceramic laminate 160 is interposed between the metal plates 152A,152B and the hole 130 is closed thereby to provide a hybrid laminate162. In this procedure, when the piezoelectric/electrostrictive elements18 a, 18 b are stuck to the surfaces of the bonded metal plates 152A,152B, the hole 130 is optionally filled with a filler material 164 asshown in FIG. 39 so that a sufficient bonding pressure may be applied.

[0253] It is necessary to finally remove the filler material 164.Therefore, it is preferable to use a hard material which is easilydissolved in a solvent or the like. The material includes, for example,organic resin, wax, and brazing filler material. It is also possible toadopt a material obtained by mixing ceramic powder as a filler withorganic resin such as acrylic.

[0254] Subsequently, as shown in FIG. 40, thepiezoelectric/electrostrictive elements 18 a, 18 b, which areconstructed as separate members, are bonded with an epoxy adhesive tothe surfaces of the metal plates 152A, 152B of the hybrid laminate 162.The separate members of the piezoelectric/electrostrictive elements 18a, 18 b can be formed, for example, in accordance with the ceramic greensheet-laminating method.

[0255] Subsequently, the same steps as those illustrated in FIGS. 37 and38 are performed as described above to obtain thepiezoelectric/electrostrictive device 10 h according to the eighthmodified embodiment in which the piezoelectric/electrostrictive elements18 a, 18 b are formed on the thin plate sections 12 a, 12 b constitutedby the metal plates 152A, 152B, of the substrate 16D, and the movablesections 20 a, 20 b having the mutually opposing end surfaces 34 a, 34 bare formed.

[0256] When all of the substrate 16D is made of metal, for example, theportions corresponding to the ceramic laminate 160 shown in FIG. 35 areformed by means of molding. Further, thin metal materials may belaminated to form the substrate 16D in accordance with the claddingmethod.

[0257] The piezoelectric/electrostrictive device described above can beutilized as the active device including, for example, varioustransducers, various actuators, frequency region functional parts(filters), transformers, vibrators, resonators, oscillators, anddiscriminators for the communication and the power generation, as wellas the sensor element for various sensors including, for example,ultrasonic sensors, acceleration sensors, angular velocity sensors,shock sensors, and mass sensors. Especially, thepiezoelectric/electrostrictive device described above can be preferablyutilized for various actuators to be used for the mechanism foradjusting the displacement and the positioning and for adjusting theangle for various precision parts such as those of optical instrumentsand precision mechanical equipments.

[0258] It is a matter of course that the piezoelectric/electrostrictivedevice and the method for producing the same according to the presentinvention are not limited to the embodiments described above, which maybe embodied in other various forms without deviating from the gist oressential characteristics of the present invention.

What is claimed is:
 1. A piezoelectric/electrostrictive devicecomprising: a pair of mutually-opposing thin plate sections and afixation section for supporting said thin plate sections; movablesections provided at forward end portions of said pair of thin platesections; and one or more piezoelectric/electrostrictive elementsarranged on at least one thin plate section of said pair of thin platesections, wherein: any one of said movable sections and said fixationsection has mutually opposing end surfaces; and a distance between saidend surfaces is not less than a length of said movable section.
 2. Thepiezoelectric/electrostrictive device according to claim 1, wherein: anyone of said movable section and said fixation section has a cutoffsection; and a part of said cutoff section constitutes said mutuallyopposing end surfaces.
 3. The piezoelectric/electrostrictive deviceaccording to claim 1, wherein said thin plate section, said movablesection, and said fixation section are composed of a ceramic substrateintegrated into one unit by co-firing a ceramic green laminate andcutting off unnecessary portions.
 4. The piezoelectric/electrostrictivedevice according to claim 3, wherein said piezoelectric/electrostrictiveelement has a film-shaped configuration, and it is integrated with saidceramic substrate by means of sintering.
 5. Thepiezoelectric/electrostrictive device according to claim 1, wherein agap is formed between said mutually opposing end surfaces.
 6. Thepiezoelectric/electrostrictive device according to claim 1, wherein: amember which is the same as a constitutive member of any one of saidmovable section and said fixation section, or a plurality of memberswhich are different therefrom are interposed between said mutuallyopposing end surfaces; and an areal size of a surface of said memberopposed to said end surface is substantially the same as an areal sizeof said end surface.
 7. The piezoelectric/electrostrictive deviceaccording to claim 6, wherein at least one member of said plurality ofmembers is organic resin.
 8. The piezoelectric/electrostrictive deviceaccording to claim 6, wherein a hole, which is formed by both innerwalls of said pair of thin plate sections, inner walls of said movablesections, inner walls of said plurality of members, and an inner wall ofsaid fixation section, is filled with a gel material.
 9. Thepiezoelectric/electrostrictive device according to claim 1, wherein saiddevice has such a structure that internal residual stress, which hasbeen generated in said thin plate section and/or saidpiezoelectric/electrostrictive element during production, is released byforming said mutually opposing end surfaces.
 10. Thepiezoelectric/electrostrictive device according to claim 1, wherein saidpiezoelectric/electrostrictive element has apiezoelectric/electrostrictive layer and a pair of electrodes formed onsaid piezoelectric/electrostrictive layer.
 11. Thepiezoelectric/electrostrictive device according to claim 10, whereinsaid piezoelectric/electrostrictive element is constructed in a stackedform comprising a plurality of units each including saidpiezoelectric/electrostrictive layer and said pair of electrodes.
 12. Amethod for producing a piezoelectric/electrostrictive device comprising:a pair of mutually opposing thin plate sections and a fixation sectionfor supporting said thin plate sections; movable sections provided atforward end portions of said pair of thin plate sections; and one ormore piezoelectric/electrostrictive elements arranged on at least onethin plate section of said pair of thin plate sections, said methodcomprising: a step of forming said movable sections or said fixationsection having mutually opposing end surfaces wherein a distance betweensaid end surfaces is not less than a length of said movable section, bycutting off a predetermined part of any one of a portion to be formedinto said movable sections or a portion to be formed into said fixationsection after producing at least said piezoelectric/electrostrictiveelement on said thin plate section.
 13. A method for producing apiezoelectric/electrostrictive device comprising: a pair of mutuallyopposing thin plate sections and a fixation section for supporting saidthin plate sections; movable sections provided at forward end portionsof said pair of thin plate sections; and one or morepiezoelectric/electrostrictive elements arranged on at least one thinplate section of said pair of thin plate sections, said methodcomprising: a step of producing a ceramic laminate by integrallysintering a ceramic green laminate including at least a ceramic greensheet having a window and ceramic green sheets to be formed into saidthin plate sections thereafter to produce said ceramic laminate; a stepof forming said piezoelectric/electrostrictive element on an outersurface of a portion of said ceramic laminate to be formed into saidthin plate section; and a cutoff step of forming said movable sectionsor said fixation section having at least mutually opposing end surfaceswherein a distance between said end surfaces is not less than a lengthof said movable section, by means of at least one time of cutofftreatment for said ceramic laminate formed with saidpiezoelectric/electrostrictive element.
 14. The method for producingsaid piezoelectric/electrostrictive device according to claim 13,wherein: in said step of producing said ceramic laminate, said ceramiclaminate is produced by integrally sintering a ceramic green laminateincluding a plurality of ceramic green sheets each having a window forforming said movable section or said fixation section having at leastsaid mutually opposing end surfaces, and said ceramic green sheets to beformed into said thin plate sections thereafter to produce said ceramiclaminate; and in said cutoff step, said movable section or said fixationsection, which has at least said mutually opposing end surfaces and inwhich said distance between said end surfaces is not less than saidlength of said movable section, is formed by means of said cutofftreatment for said ceramic laminate formed with saidpiezoelectric/electrostrictive element.
 15. The method for producingsaid piezoelectric/electrostrictive device according to claim 13,wherein: in said step of producing said ceramic laminate, said ceramiclaminate is produced by integrally sintering a ceramic green laminateincluding a plurality of ceramic green sheets each having a window forforming a portion to be formed into said movable section or a portion tobe formed into said fixation section having at least said mutuallyopposing end surfaces partially connected to one another, and saidceramic green sheets to be formed into said thin plate sectionsthereafter to produce said ceramic laminate; and in said cutoff step,said portion to be formed into said movable section or said portion tobe formed into said fixation section having at least said mutuallyopposing end surfaces partially connected to one another is formed bymeans of said cutoff treatment for said ceramic laminate formed withsaid piezoelectric/electrostrictive element, and said movable section orsaid fixation section, which has said mutually opposing end surfaces andin which said distance between said end surfaces is not less than saidlength of said movable section, is formed by cutting off said connectingportion.
 16. The method for producing saidpiezoelectric/electrostrictive device according to claim 12, furthercomprising a step of allowing a plurality of members different from aconstitutive member of said movable section or said fixation section tointervene between said mutually opposing end surfaces.
 17. The methodfor producing said piezoelectric/electrostrictive device according toclaim 16, wherein organic resin is used as at least one member of saidplurality of members.